They explained a reason for this back in vanilla Naxx with Atiesh in a blue post. The game doesn’t differentiate a tradeable fragment from a non tradeable fragment because they all go in the same stack, as such any stackable BoP items are not tradeable. I understand that it will probably cause some guilds to lose a fragment or two if they didn’t play during vanilla unfortunately, However, it was explained via a blue post and we had no reason to expect it to behave differently now. Scroll down to the section on Naxxramas in this blue post. WoW Classic Era - “Not A Bug” List - Updated April 22, 2021