Its absolutely relevant since it makes it clear what stacks and what doesn’t. It says that “% Reduced target’s Elemental Resistances” cannot stack, and that you pick the highest. If he’s looking to work multiple sources of resistance reduction for multiplayer, it could be relevant and helpful to provide this info.
Sure, you answered his question already with a simple “no”, but to say that my reply had nothing to do with his question is wrong.
Actually, his question was whether the same skill/debuff would stack with itself; which is what Ceno answered to. Your link is relevant to resist reductions as a whole, but not to the question of whether the same debuff would stack with itself.