Today, I was able to activate my PW on XM. I did need to reach out to have a line activated and tied to the IMEI of my watch and phone number. To test, I turned off my phone and made a couple of calls from my watch which is also paired to my Pixel Buds. Working well this far. Did not see this advertised on XM but read about it on another site.
Cheers ...
Config: Pixel 6 Pro with gen1 Pixel Watch
Cheers ...
Config: Pixel 6 Pro with gen1 Pixel Watch