It does absorb the oil during use. Yet, with careful, conservative use it will go a long time before saturation. I did boil one of my Norton India stones but not so much to remove the oil it was to clean the surface. Still, I don't have a newer stone which I've seen come with a heavy oil like vasoline on it. Should I have one of those I'd promptly boil it, then use soapy H2O or a judicious amount of light oil when sharpening.
Those waterstones take some getting used to unless your an experienced sharpener. This decision is not this complicated. You need to sharpen and gain some experience. DM