Google Pixel 6 and 6 pro 5G SA and NSA support will come. To M1 in Jun 2022 firmware update. That means volte and vowifi should be available on previous pixel phones with new firmwares update. We are hopeful that the update will also be available on the Pixel 4 series so that M1 users will get VoLTE/VoWIFI feature provisioned.
As for TPG, Pixel users will have to rely on TPG voice app to make and receive calls as there is no indication that Google is enabling this feature for TPG users. The VoLTE Provisioning is necessary so that TPG users can make and receive calls over VoLTE as it doesn’t have a 3G network to fall back to.