[thaumasiotes]

No one believes now, or ever has believed, that the person paying a phone bill is the same person who uses the phone. That's not the way money works.

[kazinator]

According to the bizarre anecdote in this HN submission, the person who pays for the phone bill must be the person who is validating a YouTube account with that phone number.

Validating an account with a phone number constitutes phone use so, yes, Google and Youtube have shown an instance of belief that the person paying is the same as the person who uses.