Can ADO REST API link branch to a work item and have it auto displayed in pull request for that branch?

I successfully call ADO REST API to link a branch (let's call it "target") to a work item, after that I create a pull request from ADO web portal from a private branch to "target" branch, I expect the web page show the work item linked to the pull request, unfortunately not.
I know the work item could be linked to the pull request automatically. If the branch is linked to the work item from web portal, say editing the work item in links, or upon creating the branch add the work item to the new branch, then the pull request creation page will show that work item automatically linked to the pull request.
My question is what is missing in calling ADO REST API so that the linkage done by REST API doesn't enable the auto work item link to pull request?
The REST API I call to link a branch to a work item is Work Items - Update, the payload used is like the post.
Meanwhile I know from ADO web portal, upon creating branch with work item linked, the REST API called is not the one I used above, instead /_api/wit/$batch with payload as PATCH method with similar payload in work items update. I don't know what makes difference from the black box but there must be something making differences here.

I'd like to find the way to call ADO REST API so that the work item linked to the branch could be also linked automatically to pull request creation web page.

Turns out there's a simple fix by adding the "#work item ID" to the comment of the commit in that branch and ADO just does the remained.