[Timely] Accessibility vs validation on WCAG 3

I have to remind everyone that our previous publication of WCAG 3 had 
HTML validation errors for which we were granted a one-time exception to 
be allowed to publish. We set role="region" on the <details> element to 
get it identified as separate content, but HTML doesn't allow that 
(there may be an issue to file on HTML). I also have the script putting 
in a "end of <whatever>" at the bottom of each <details>, so it may meet 
the need. We also used @summary on <table> to provide a more 
contextualized title for it for text users, but HTML no longer allows that.

I am open to statements of "this feature is essential notwithstanding 
being non-valid HTML, because no other feature accomplishes the goal", 
or alternate proposals for how to meet the needs in valid HTML. If I 
don't get a clear answer before publication, my edits will be to:

  * Remove @role on <details>
  * Convert @summary to <caption> and use CSS to hide from visible screen

Michael