Question about aria-required and inherited role mapping

Hi,

This came up today and I found something in the spec I was unclear on.

 

According to:

https://w3c.github.io/aria/#aria-required

 

Within the "Used in Roles" list, it states role=radiogroup as supported. The
result being that using aria-required="true" on role=radiogroup will cause
all child radios to be flagged as required.

 

Since role=radiogroup is implicitly the same as a fieldset, and role=group
is the same, why is role=group not included within this list?

 

Thanks,

Bryan