Who chooses the size for a protected audience auction (PAA)—the Publisher, Top Seller, or Chrome internal logic?

[pm-harshad-mane]

When an ad-slot backs various sizes like A, B, and C, the PA only backs one size at a time.
It seems that Chrome has the ability to check the available IGs on a device and the supported ad sizes for each IG in this situation.
Who chooses the size for a protected audience auction (PAA)—the Publisher, Top Seller, or Chrome internal logic?
Can the Privacy Sandbox standardize the supported size consistent in PA to prevent potential data leaks caused by random ad sizes that could identify a user?

[rdgordon-index]

cf. https://github.com/google/ads-privacy/tree/master/proposals/fledge-multiple-seller-testing#faq

[rdgordon-index]

Given all the other changes related to sizes -- for example, #928 -- have we made any headway on this topic?