Photoshop won't let go of images it no longe edits

Why should Photoshop unlock the file if you have a document open for the files content in Photoshop.  Photoshop assumes the you may want to update that files or you  will want to be able to refresh revert the document.  Photoshop should hold a lock on the file as long as a document for it is open in Photoshop.  Other Application should not be able to delete or update the fie while it is open in Photoshop.   If Photoshop does unlock the file when you close out the document that would be an issue.  How have you determined that Photoshop has not release the file. If Photoshop crashes you system should release all locks photoshop had,  Over the years running Windows I have had files the have become locked that I could not get unlock when I had no open programs.  I was never able to determine what had the lock.  All I could do was sign out of Windows and sign back in.  I could not prove what Programs had locked the file. I closed ever program I  was running. I think some system background task for my user id must have held the lock. For when I sign back in it was unlocked.

This is a user Forum, so you are not really addressing Adobe here, even though some Adobe employees thankfully have been dropping by.

I am on Mac, so I cannot reproduce the issue. 

Are you working locally or across a network? 

I am dubious whether it is a Photoshop Bug but the place for Photoshop-related Bug Reports is

Photoshop Family