Indeed, it works like freenet IRC where you have to make an account first then log in to it with Tor. This is solved by making a throwaway VPS or virtual desktop you ssh into with Tor, make your account, shred the VPS and then change the password when you log in directly to Fb with Tor.

You can also edit Torrc to temporarily only use your own Tor exit nodes if worried about malicious exits while setting up accounts.