I've been using the FB ID and password, but like you, for much over a month a PIN code has been needed anyway. What is irritating is that there is no pattern to if I am offered my email or phone to receive the PIN on, or even both. A couple of weeks ago, suddenly my email completely vanished and only the phone would show. All while I was unable to go on to roaming for some time to receive a code. The authenticators would solve this, but I still prefer not having to use those since I do need a way to share access to accounts with my family. For the moment, we use an email distribution group to get the PIN to me and my family members' account. If the authenticator becomes required, at least with Google authenticator I'll need to see if I can pass the QR code to each of us (as I've done for some other accounts).

In my personal case, I wish they would just allow FB users to designate "managers". Family accounts managers wouldn't be enough for this since only two adults can be in a family.