The problem is that the formats available when saving keep changing based on current document content.
This confuses newer users. "Why can't I save as JPEG when I could save as JPEG literally 5 minutes ago?". I have seen many different users encountering this, and when having Photoshop classes it is something I have to spend extra time explaining – when it really shouldn't be needed.
It also doesn't really make intuitive sense that "Save As" and "Save a Copy" would present the user with different file formats (sometimes). This new behaviour doesn't match behavior in any other programs like Illustrator and is unintuitive/inconsistent (doesn't match user expectations). In short, while a neat idea, the change is bad UX and should be reverted.
Since the new change was introduced:
I see users not understand how to save as file formats like JPEG/PNG
I see users confused by the available formats being different every time they try to save
I see users thinking they need to use Export As to save as JPEG/PNG, (and then losing metadata like PPI information, or encountering slowdowns on large files), never noticing that "Save a Copy" offers more formats.
I see users being super annoyed that they need to choose Save a Copy, and then remove"Copy" from the name every time, slowing them down.
I see users being worried that "Save a Copy" is somehow different than "Save As" and that quality might suffer or something.
I know there has been wishes from users for many years to be able to shorten the listen of formats available by adding a preference to hide rarely used formats or something, but the current solution to keep the list of formats change depending on file contents is only causing new confusion and inconsistent behavior.