The actual issue for me with being unable to use VoLTE is the lack of mbn file for any of the three operators here. Sadly this probably means that VoWiFi cannot be a band-aid for no VoLTE.
I assume that the VoWiFi is a modem function, and will also be dependent on the mbn file.
That said, VoWiFi is important at my home for reliable operation, without it I frequently have to go outside on the street.