Applying replace file

I’m asking this question as a bug, but if not, you can even remove it.

I created a form that has a file option for the thumbnail, and everything works correctly.
In another form to edit the post, I added the replace file option, which would be to replace instead of adding another file.
The issue is, when I apply it to change the image it changes it on the front, but on the back it doesn’t replace the image, it just adds the new image normally.
Would this replace file function have to replace the old file with the new one or does it add another image to maintain the old one? I thought I would replace the media instead of adding new one.

Grateful for the attention.
replace img pro form