Well yeah. In AD&D only people who like disappointment or aren't rolling for their stats pick character details before they generate their #s.
You need the stats in order to see what the rest of your options are (or aren't).
I suppose it's happened.
Afterall, I just rolled up a 1/2ling barbarian for our PF game. 1/2lings there have a -2 on str. So I put the one & only 18 I rolled into str - knowing it'd drop to a 16.
If it were only about the #s, then logic would dictate that 1) my barbarian would NOT be a 1/2ling, 2) In fact I'd pick a race that boosted str.
I've never actually played AD&D, but the people who have told me that they often asked their players what they wanted to play and made sure the stats matched the requirement. And if that meant boosting a stat to 17 (Paladin) then so be it.
It really depends on what and how you're playing. For example, my last few campaigns were very character-driven despite playing "gamesy" systems like PF or 4e. Which meant I often talked with the GM about the setting, the general directon and my character ideas (along with an elaborated background story) before throwing any die or even knowing my class. So if I wanted to play a female fighter/warrior who focused on strength and dexterity and wisdom (one of my PCs), I would have decided this before knowing my abilities or stat array. Because I want to play a person first, and fun mechanics second.