Why not? It still limits bot creation (same number can only be used every 6 months). They don't actually want to know if the number belongs to you. Not much different than using a burner number.
> Not everyone has a friend with a phone that doesn't use discord that they can use.
I believe Discord can afford to ignore those 3 people. Not saying it's convenient for the user, but it's not enough of an issue to encourage Discord to find a solution.