You're missing the point. Neither Phone number of Email address/username solve the problem you're proposing. But an email address/username is a lot more transie

You're missing the point. Neither Phone number of Email address/username solve the problem you're proposing. But an email address/username is a lot more transient than a phone number. I can change emails/usernames very easily and with little effort, and while burner numbers and applications that help that exist, changing phone numbers is not as easy and thus a significant percentage of users are unlikely to do it regularly. So you have a pseudo real ID that to the end user FEELS like it isn't you, but is a very strong (no pun intended) signal that it is to anyone looking in. The phone number grants no you special verification of identity over an email address that doesn't involve an external verification mechanism (i.e, talking to the identity in person.)