Yup, you can read my whole figuring it out here:
Tl;Dr, Both were working on the global rom as of last january when I got the phone, after switching to xioami.eu, it was necessary to restore a backup of the modem taken with firmware from the global rom flashed, which worked fine for a while.
At some point relatively recently (past couple months) I forgot to do the whole restore modem charade and volte/vowifi were just working. Last weeks weekly had volte/vowifi both working with nothing extra, BUT, I couldn't place calls, only receive (placing calls gave me an audio message "your carrier does not allow this call), I could place calls fine with volte turned off.
I suspect this issue had actually existed ever since volte "started working" in the base weekly, as I recall sometime in december running in to this same issue with the calls, I just don't place enough calls in general to say for sure. What I can say is the calling issue cleared up in 21.1.20 after restoring the modem like I did for older weeklies.
This weekly, no volte or vowifi, no IMS registration, I tried the before mentioned modem trick that worked in the older weeklys and no dice on that either.
Sim info is sim1: USA T-Mobile, sim2: Ultra Mobile (T-Mobile mvno)