For people with multiple battle.net - do you have to create / get new email addresses for each ?

seems that using some of the public email providers just to get different logins is annoying (and not good for security) - on the other hand as I reactivated thanks to the "free 7 days" anniversary offer - I just got hit by the really annoying "can't use my authenticator to log in all 5 windows at once" - that makes the login process annoying and maybe splitting into individual accounts would help for that