@PPakalns says in #21247 (comment):

I still do not like how Radio widgets and RadioGroup works. It would be better for each widget to have separate events. But I could partially override behavior with my own. RadioButtons and RadioGroup shouldn't make assumptions that there is exactly one active radio button.

They also note:

In my opinion current radio button / radio group design tries to assume too much about how widgets will be used. I would suggest that each radio button should behave similarly to toggle, checkbox. And radio group is optional thing that users can use on top of group of radio buttons if they want to.
Current approach is hard to integrate with tools that can handle radio button management separately.