Should we explicitly clarify that required accessible parent/children relationships do not apply to elements with aria-busy="true"?

It seems understandable, but I don’t see a place where this is clearly stated. As it stands, tool vendors might still enforce these relationships even when aria-busy is set.

Side note:

I’ve noticed inconsistencies in how browsers handle elements with aria-busy="true". Some treat the role as generic, while others retain the role and announce "busy." What’s the expected behavior? @cookiecrook, would this be a good candidate for WPT?