Board Thread:Versus Battles/@comment-31372267-20181103161101/@comment-28876888-20181103213022

Largely game mechanics. It was discussed a whike back, but generally, it sums up to "resistances get better over time, but the entire d20 system is game mechanics"

otherwise you could argue a Goblin resists 2-A mindhax because of a 1/20 chance. So it is game mechanics.