SharePoint - Stop sharing - new behavior or new bug?

It used to be possible for a user with Contribute permission in a library to upload a file, share it, and the stop sharing it.

The result of sharing the file would be that unique permisions then apply to the file. That is, it would no longer inherit permissions from its parent container.

If the user then stopped sharing the file, permisisons would be reset and again inherit permissions.

This behavior has very recently changed. The person with Contribute permission who shared it can no longer stop sharing it (the Stop sharing button is grayed out).

Only someone with Full Control permission can stop sharing it, and if they do, permissions for all members are removed from the fiile except for the site owners group. 

A user reported this new behavior to me after accidentally sharing with the wrong person, and being unable to undo their mistake.

Anyone else concur with my understanding of this being a new behavior?