<…> I wonder though, didn't the Merit airdrops achieve the same thing? For example, newbie accounts instantly become Member.
Not really. The Merits airdropped to each account were in accordance to the amount they needed to maintain there rank at the time the Merit System kicked-in (with some Hero exceptions that where airdropped 1K Merits instead of 500 Merits). A Newbie would have remained a Newbie.