Prioritize .onion hosts in AltSvc?

We now support AltSvc and Mahrud suggested we might want to prioritize .onion AltSvc hosts in Tor Browser. It's an interesting idea and I would need to think about it more to know if it's desirable. Mahrud also pointed out a web page that demonstrates AltSvc over .onion:

https://perfectoid.space/test.php

Refresh several times and it will turn green when .onion is being used.