That isn't signing up, that is filling out a profile and/or stating/proving who you are (for payment processing & fraud prevention purposes). While it is often

That isn't signing up, that is filling out a profile and/or stating/proving who you are (for payment processing & fraud prevention purposes). While it is often closely linked to “signing up” it is not actually a direct part of it. Even if you consider it all to be part of the sign-up, it could be a single form so the match of “as many forms to cancel as to sign-up” still works: this one form for signing up, the “are you sure, this is why you might prefer not to” page being its opposite at the other end.