Just say “because blizzard decided” and never go more into it because it doesn’t make any sense. I once saw someone with a nice 1h axe, looked into it, turns out it dropped from a rare in Ardenweald called somethingflayer. So I went to the location, didn’t get it, “no big deal” I said, “it will eventually since it is 1h axe and I’m a rogue.” Turns out that 1h axe only drops frost dk, fury and prot warrior and pro paladins only. So I researched more into this madness then got hit with strength vs agility vs intellect drop rule, I never noped out of that rabbit hole so fast in my life.
Trust me, for your own sanity just say “because blizzard decided” and move on.