I did not do the full installer for todays update. Only the 40MB OTA. Kind of wish I did the full installer, would have saved me a lot of time.
10.3.2 -> 10.3.3 doesn't require full installer. And the fact that B6 -> Final didn't require full installer shows that B6 was a final candidate.
So it sounds like apple make beta testers do the full installer when they think they're close to a Gm, presumably to overwrite the previous beta tested versions, but don't make users do them going from public versions