You don't say how long your pw is; and I don't know how many tries, how quickly, FB allows. That's the only hole I see at a glance. I'm feeling 12 characters is now too low.
longer than that, that's for sure. And I'd presume FB has rate-per-minute limits of attempts?
That seems unlikely for a high entropy password.
If there's no salted database of passwords to crack, and some limit on tries, I agree. We don't know what he means by "unique" though. Maybe not truly high entropy.
What I didn't take into account was passwords saved in/by the browser - and there are new adverse developments there, IIRC.