Can’t replace Icon

In version 3.9 (411), if I take an icon using the built-in picture-taking icon-thing, I can’t seem to ever get rid of it.

If I import a different image and name it “Icon”, it will not be visible in Assets—the first version will still be there.

And on the project screen, it will also be the original icon.

[edited because in the first version I was wrong about a thing]