This does work on Pixel's, but Google allowed carriers to block it, which at least one major US carrier does.

It would be great if google could dick swing on carriers with the same might as Apple

This is the “Backup calling” toggle in Pixel IMS, and carriers are fond of blocking that function.

(TIL: Vo“WiFi” over wired Ethernet over USB doesn’t work on AOSP or Pixel and never did, for no apparent reason except noöne caring to make it work.)

The part that does not work on iOS is putting SIM2 into airplane mode so that it can do VoWiFi without connecting to the network. That would reduce power consumption and avoid utterly obnoxious behavior on the part of some carriers (cough, Visible).