Honestly, that’s still just a version of the frosting essentially. I feel like it would be weird to have that in the middle of a button when, then immediately go to the blurry translucent glass, and then immediately after that is the shiny outer rim of the button. In title bars it works a little better since there’s a lot of room on either side of the text.
But all that said, I’m not a designer, so maybe they could make it work. I just know that from my many years working with designers, they always tried to avoid using dropshadows like that unless there was no other solution.