Accessibility attributes in WCAG 3

For the WCAG 3 FPWD, we put in a bit of code to improve accessibility:

  * On the <details> element, we put role="region".
  * On rating tables, we put summary attributes for the title to avoid
    redundant visual titles with the <summary> element of the parent
    <details> element, since in the table context that wasn't being
    picked up.

Both these are rejected by the HTML validator. <details> only allows 
role="group", and tables no longer allow summary attributes.

PLH allowed publication because we discovered this last minute and he 
didn't want to hold us back further. But he told me next round, it won't 
be allowed unless I can provide substantial info about why we can't use 
valid code, with time for review before publication.

So first question is, do we need these features? If we put role="group" 
on <details>, will it accomplish the same thing? Do we need a role 
attribute at all? For the table summary, maybe we should use aria-label 
or something?

If valid code won't work, I'll need to make a stronger case about why we 
absolutely have to use non-valid code.

Michael