Here’s the editor with a featured image set.
Click either pencil icon to edit the featured image. The media model opens to this:
There is no indication of the current featured image nor is there an edit button. If I was coming in here to edit the featured image, either the image itself or its meta, I would be lacking sign posts for my flow.
Further, Calypso lacks an “uploaded to this post” filter. This makes finding previously uploaded featured images all the harder.
If the modal were to open with the current featured image selected, an edit button would show.
That marks the way more clearly for those wanting to edit the current featured image rather than swap in a new image.