I have 7 Motiv balls, the Raptor Talon, all the Sigmas, three Venoms (Strike, Shock, & Toxin). Really never got any oil from any of them.
If the coverstocks were designed to "hold" the oil and not expel it even under heat, then I would expect a loss in reaction. That has never happened to me. All I ever do is resurface and the balls continue to perform.
Motiv covers seem to be harder than most. You can sense/feel it when resurfacing. Perhaps they just don't absorb oil like we expect from a modern bowling ball. So I guess that means they are not stripping oil from the lane, but actually pushing the oil around and causing carrydown.
But, I believe Joe S. stated there is no such thing as carry down, so