Some .tor.onion sites are not displaying the underlying V3 onion address in alpha

In Tor Browser 12.5 we display the corresponding V3 onion address in the circuit display when visiting a SecureDrop instance via its human-readable .tor.onion address. However I've noticed it's not working on certain .tor.onion addresses, e.g.:

• Working as expected: https://nytimes.securedrop.tor.onion/
• Does not work: http://abc.au.securedrop.tor.onion/

Could the double subdomain be the cause?

(Given this is a bug with a recently developed 12.5 feature, I'd like to Backport the fix after 12.5 stable's release if possible please)