Querying foreign keys different results

I am writing some code that will disable and enable foreign keys on a table. It appears to run fine. When I check the status of the Foreign key immediately executing the code the status appears to be unchanged with one query and changed with a different query.

I can't seem to figure out what the problem is and was hoping someone can help me out and explain this anomaly and or suggest a fix to my code.

Below is my test CASE along with sample data to show what I have done.

CREATE TABLE customers 
(CUSTOMER_ID, FIRST_NAME, LAST_NAME) AS
SELECT 1, 'Faith', 'Mazzarone' FROM DUAL UNION ALL
SELECT 2, 'Lisa', 'Saladino' FROM DUAL UNION ALL
SELECT 3, 'Micheal', 'Palmice' FROM DUAL UNION ALL
SELECT 4, 'Joseph', 'Zaza' FROM DUAL UNION ALL
SELECT 5, 'Jerry', 'Torchiano' FROM DUAL;

ALTER TABLE customers 
ADD CONSTRAINT customers_pk PRIMARY KEY (customer_id);

CREATE TABLE items 
(PRODUCT_ID, PRODUCT_NAME, PRICE) AS
SELECT 100, 'Black Shoes', 79.99 FROM DUAL UNION ALL
SELECT 101, 'Brown Pants', 111.99 FROM DUAL UNION ALL
SELECT 102, 'White Shirt', 10.99 FROM DUAL;

ALTER TABLE items 
ADD CONSTRAINT items_pk PRIMARY KEY (product_id);

create table purchases(
  ORDER_ID NUMBER GENERATED BY DEFAULT AS IDENTITY (START WITH 1) NOT NULL,
  customer_id   number, 
  PRODUCT_ID NUMBER, 
  QUANTITY NUMBER, 
  purchase_date timestamp
);

insert  into purchases (customer_id, product_id, quantity, purchase_date) 
SELECT 3, 102, 4,TIMESTAMP '2022-12-22 21:44:35' + NUMTODSINTERVAL ( LEVEL * 2, 'DAY') FROM    dual
CONNECT BY  LEVEL <= 15 UNION ALL 
select 1, 101,3, date '2023-03-29' + level * interval '2' day from dual
          connect by level <= 12
union all
select 2, 101,2, date '2023-01-15' + level * interval '8' hour from dual
          connect by level <= 15
union all
select 2, 102,2,date '2023-04-13' + level * interval '1 1' day to hour from dual
          connect by level <= 11
union all
select 3, 101,2, date '2023-02-01' + level * interval '1 05:03' day to minute from dual
          connect by level <= 10
union all
select 3, 101,1, date '2023-04-22' + level * interval '23' hour from dual
          connect by level <= 23
union all
select 3, 100,1,  date '2022-03-01' + level * interval '1 00:23:05' day to second from dual
          connect by level <= 15
union all
select 4, 102,1, date '2023-01-01' + level * interval '5' hour from dual
          connect by level <= 60;

ALTER TABLE purchases 
ADD CONSTRAINT order_pk PRIMARY KEY (order_id);

ALTER TABLE purchases ADD CONSTRAINT customers_fk FOREIGN KEY (customer_id) REFERENCES customers(customer_id);

ALTER TABLE purchases ADD CONSTRAINT items_fk FOREIGN KEY (PRODUCT_ID) REFERENCES items(product_id);

/* both queries fine here */

SELECT '"' || a.owner
                    || '"."'
                    || a.table_name
                    || '"' AS full_table_name,
                a.constraint_name,
                b.status
            FROM user_constraints a
            JOIN user_constraints b
                ON ( a.r_constraint_name = b.constraint_name
                    AND a.r_owner = b.owner )
            WHERE a.constraint_type = 'R'
                AND b.status = 'ENABLED'
            ORDER BY 1

FULL_TABLE_NAME
	CONSTRAINT_NAME	STATUS
"XXX"."PURCHASES"	ITEMS_FK	ENABLED
"XXX"."PURCHASES"	CUSTOMERS_FK	ENABLED

select owner, table_name, r_constraint_name, status
 from user_constraints
where constraint_type = 'R';

OWNER	TABLE_NAME	R_CONSTRAINT_NAME	STATUS
XXX	PURCHASES	CUSTOMERS_PK	ENABLED
XXX	PURCHASES	ITEMS_PK	ENABLED

/* disable foreign keys */

BEGIN
    FOR r IN (
        SELECT '"' || a.owner
                    || '"."'
                    || a.table_name
                    || '"' AS full_table_name,
                a.constraint_name
            FROM user_constraints a
            JOIN user_constraints b
                ON ( a.r_constraint_name = b.constraint_name
                    AND a.r_owner = b.owner )
            WHERE a.constraint_type = 'R'
                AND b.status = 'ENABLED'
            ORDER BY 1 )  LOOP
            
        dbms_output.put_line ( 'Disable the constraint ' || r.constraint_name ||' (on table ' || r.full_table_name || ')' ) ;
        dbms_utility.exec_ddl_statement ( 'alter table ' || r.full_table_name || ' disable constraint ' || r.constraint_name ) ;
        
    END LOOP ;
END ;
/

Statement processed.
Disable the constraint ITEMS_FK (on table "XXX"."PURCHASES")
Disable the constraint CUSTOMERS_FK (on table "XXX"."PURCHASES")

/* status different between queries ????. Problem here!!!
*/

SELECT '"' || a.owner
                    || '"."'
                    || a.table_name
                    || '"' AS full_table_name,
                a.constraint_name,
                b.status
            FROM user_constraints a
            JOIN user_constraints b
                ON ( a.r_constraint_name = b.constraint_name
                    AND a.r_owner = b.owner )
            WHERE a.constraint_type = 'R'
                AND b.status = 'ENABLED'
            ORDER BY 1

FULL_TABLE_NAME
	CONSTRAINT_NAME	STATUS
"XXX"."PURCHASES"	ITEMS_FK	ENABLED
"XXX"."PURCHASES"	CUSTOMERS_FK	ENABLED

select owner, table_name, r_constraint_name, status
 from user_constraints
where constraint_type = 'R';

OWNER	TABLE_NAME	R_CONSTRAINT_NAME	STATUS
XXX	PURCHASES	CUSTOMERS_PK	DISABLED
XXX	PURCHASES	ITEMS_PK	DISABLED

Those are 2 different queries and they are correctly showing the results.
you're assuming that you are seeing the status of the foreign key constraint but... that is not the case. Add some additional columns to the query and it all becomes clear.

SELECT '"' || a.owner
                    || '"."'
                    || a.table_name
                    || '"' AS full_table_name,
                a.constraint_name,
                a.status,
                b.constraint_name, 
                b.table_name, 
                b.status
            FROM user_constraints a
            JOIN user_constraints b
                ON ( a.r_constraint_name = b.constraint_name
                    AND a.r_owner = b.owner )
            WHERE a.constraint_type = 'R'
                AND b.status = 'ENABLED'
            ORDER BY 1;

"ACDC"."PURCHASES"	ITEMS_FK	  DISABLED  ITEMS_PK	    ITEMS	    ENABLED
"ACDC"."PURCHASES"	CUSTOMERS_FK. DISABLED	CUSTOMERS_PK	CUSTOMERS	ENABLED

The column b.status is the status of the referenced constraint, not the status of the foreign key constraint. The referenced constraint is the primary key value of the 2 tables and the status is "enabled" since you didn't touch those....

To find referenced constraints, just use that other query you are showing

select owner, table_name, r_constraint_name, status
 from user_constraints
where constraint_type = 'R';

But... I would not take this route. What if there is a constraint that is already disabled before you run your script ? That constraint will then be enabled again by your "enable" script. Much safer to create a table where you store the name of the constraints you have disabled so you know which ones to enable again afterwards.