Its not. You have to kill the boss before you get access to its loot table. Thats not how deterministic gearing works
You uphold the integrity by requiring the player to do the raiding (mythic), in order to get the items (mythic).
Hero gear is a dime a dozen. Acquired by delves even
looke at 640 alt who picked up a hero track m+ trinket today from doing m+
Has everything to do with it