4 points
I work in telecommunications. This is pretty much exactly correct.
Not really a rebuttal to anything you said, but to expand on the fact that WiFi calling uses VoLTE “most of the time”, which is true because in some conditions SIP is used, but if you are using an Android or iOS phone, you are always using a modem, the voice line is never analog, and all digital voice communications are sent over TCP/IP.