Because there is also a very awesome boss named Kilgardan (homophonic egg).
Because of the delay in opening WLK, these two BOSS are killed by egg-hurting players thousands of times a week (it is said that Illidan is applying for overtime pay from Netease because he has to run hundreds of times a day to repair weapons).
No one wants to enter their full name when typing. Too much trouble.
To sum up, we all agree that the same name is Brother Egg.