i'm curious, what makes GSP's BJJ elite?
his credentials outside of MMA are not exactly stellar. he dominated people on the ground brilliantly, but rarely showed much of pure BJJ in his fights. the best argument to make regarding his BJJ being high level is the fact that he passed penn's guard - and that is impressive - but penn was a lot smaller and took a beating first if i recall correctly.
bottom line is, if GSP grappled with durinho, he'd be in trouble instantly. now, i'd pick prime GSP over burns and usman, but that doesn't mean that his BJJ was much better than kamaru's. they're both black belts, they've both shown excellent control on the mat, they both use BJJ to complement their wrestling games, and neither one of them has any credentials to prove they have truly elite BJJ.
arona is arguably one of the best (or at least most effective) no-gi ground fighters in history. i know you were being intentionally hyperbolic to make a point, but there are people actually fighting in MMA who deserve to be mentioned as his peers in that category. GSP isn't one of them.