It seems this site relies on a check for the domains' AAAA records to see if they support IPv6. Doesn't have anything to do with IPv6 in the products/apps that those sites offer.
We should have both, that's the point, to which you replied that "the site's intent is to show the general population's ability to organically reach those sites". I disagree with you, for many of those apps having only the website's status in the dashboard is insufficient.