I copied your form then added a button to it (command55) and got that flat style you're using. I played with styles to see if I could replicate what you have & ended up with what's there, but not normal to me. There seems to be no way to change its style to what I normally see by using the property sheet or ribbon. So I opened a new form in design and added a button and got the style I'm used to and pasted that onto the copied form. It retained its style. So why does that form enforce the flat style yet a new form does not? If you didn't create that style from the ribbon then where does it come from? Puzzling. Regardless, command0 exhibits the same behaviour as your original buttons.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.