So, looks like WB:FMAG elves can't be Thieves using the RAW? Obviously it's a simple matter of waving a hand and allowing it in your game; I was just curious if there was a design decision at work.
The thief wasn't officially a thing until the Greyhawk supplement came out: being based on just the first three booklets from the original version of Dungeons & Dragons (1974), Elves are a blend of fighter and magic-user.
I understand that, but the rules include the Thief as an option for Dwarves and Halflings (so, not a "pure" 3 LBB game), so why not Elves? Again, just wondering.
Well to be honest, I didn't spend a lot of time thinking about this. I just thought elves already have the fighter and wizard thing and maybe thieves don't really fit their nature. So I added the thief to the halfling and dwarf to give them something else and that was that.