Petrolatum and gasoline are not the same. They're both products of fractional distillation of crude oil but not the same, no more than glucose and fructose are the same (you can get both from the same fruit), or oleic and ricinoleic acid (you can fractionate both from castor oil), or fat and meat (you can get both from the same animal). It's very bad science to say they are the same.
Also mineral oil isn't harmful to the skin. Cosmetic grade mineral oil is noncomedogenic (see DiNardo, J.C. Is mineral oil comedogenic? J. Cosmet. Dermatol. 4, 2–3 (2005) if you have access to the Wiley online library. If you know someone in college they might have access to the database through their library). It is, in fact, beneficial even though it also has an unpleasant skin feel. Vaseline, in particular, is an excellent barrier agent but feels gross on the skin.
As for the primer, it feels very nice because it has a lot of emollients (the usual selection of silicones plus some very nice plant oils), occlusive agents that protect the skin from water loss and Silica, which is an anti caking agent. I'm quite impressed with the formula, in fact, it's very skin friendly with lots of emollients and humectants. It's certainly an improvement over straight-up silicone if your skin is not in tip-top shape.
