privaterelay.appleid.com e-mail addresses aren’t forwarding

While Hide My E-mail addresses, the one created manually, which have an @icloud.com domain, work just fine, the E-mail addresses created as part of Sign-in With AppleID, which have an @privaterelay.appleid.com do not work.

First I suspected that maybe they reject all mail not coming from the same domain as the one one signed up with, but I recently created a tailscale account, and signing up with the same e-mail in the tailscale user forums, which are using the same tailscale.com domain, doesn’t result in me getting the confirmation e-mail.

This is rather concerning, because I have no idea how many e-mails (dozens, hundreds, …?) I may not have received, because the relaying of these addresses doesn’t work. And this seems to be an ongoing thing, with messages about this issue here stretching back YEARS.

Is this EVER going to get fixed?