Do User Explorer reports in GA4 automatically hide user_id when filtering by purchase revenue?

It appears I am only able to view user_id's OR purchase revenue in GA4 User Explorer reports.

I am wondering if this is the expected functionality? (Is it to prevent me from filtering by revenue to find a specific transaction and specific user? We are already unable to search for a specific user_id value like we could in GA Universal)

When I filter the report by purchase revenue>$0, I am only able to see anonymous identifiers in the user_id (app instance ID) column.
example of seeing purchase revenue with no user_id

When I am not filtering by purchase revenue, I can see true user_id values, but the purchase revenue column does not populate.
example of seeing user_id with no purchase revenue

If I try to force the issue and filter by "signed in with user_id = yes" AND "purchase_revenue > $0", the report returns no data.

I am trying to understand: is this the expected functionality from GA4 to protect privacy, or if there is some type of error? or I have not configured the report correctly?

Try looking at revenue broken out by individual purchase events. Including the user_id in your exploration may cause problems because you don't necessarily need the user_id to see unique purchases. Not just that, but you may not be getting the full picture if you add user_id's into the picture, because that data is qualified with a rentention limit (see here). This may be what you're experiencing when you query this data. Depending on your setting here, you may not see purchase revenue past a certain date if you're trying to get a user_id along with it.