I don't see any exploit. They don't use any bug of a mob or anything. Just sneak past one mob group with invisibility and rerun the same veterans and kill them.
Maybe the loot gets adjusted or they put more mobs around the veterans to make it harder, if the developers think that it's not intended to get that much loot so easily; but if anybody gets suspended for that, then ANet has really lost it.
Also, exploiting such methods in the game (obviously not intended this way) may very well be counted as an exploit and result in your account getting suspended and you losing all your items and gold.
They wont ban you for something they messed up on their end. They'll just hotfix it and move on.
Note: I used to do this when tokens dropped from chests. There's also a "jumping puzzle" south west of those two bosses, where you can get over a mountain and kill the next boss by skipping 50% of the dungeon. Obviously also unintended. Never got punished for it since it was a design flaw that they simply fixed.
Apparently they broke it again though, hah. They're really not very good at this, are they?