Additional features, settings, or issues not covered by specific Microsoft Teams categories
This is not a security measure. You can register the same phone number for 2FA on two or more different accounts (I have three, actually), and get SMS's when logging in from new places for all of them. Or you can install the Microsoft Authentication app for that security bit, if preferred.
However, Teams in a private context will not let you log in unless there is a unique phone number registered with that account.
It works perfectly for a cooperate account, but not for a private account - both my cooperate and private Microsoft account can use Teams with the same 2FA phone number. But two private accounts cannot.
So, I second the plea: Please fix!