Doesn't change the fact that world wide, it was the first guild to kill Garrosh in a legit way... It's Blizzard's World of Warcraft, not someone else modified version of the game.
Asian realms have slightly different rules, such that really benefit them in getting World First. That doesn't change the fact that
1) They didn't cheat
2) They will be, on record, the first guild to down Garrosh in the whole World.
Did they have more gear?
Doesnt matter... If it did, them should we consider the world first in West the guild who downs Garrosh with the lowest ilevel? Of course not.
First is first.
Is "Western's first" more difficult than World's First? Sure... That's why they should value this title more than World's First. :P