Hydrogenation does not change whether it is rendered fat of pigs/pork. It is simply adding hydrogen. Which is present in every drop of water you drink. You don't absorb trans fats from soap.
Hydrogenation is not creating a mixture of one chemical and some hydrogen gas, which is what you just described.
It's a chemical reaction. You end up with a different chemical.
Trans isomerism around a double bond does not occur in nature. Only cis isomerism does. The hydrogenation process used in food production only produces trans isomers. Thus the moniker "trans fat."
Some peoples' bodies react to trans hydrocarbons as foreign substances, which is to say, their immune system responds as if it were dangerous, and voila...rashes or worse.
My daughter and I happen to be two people who react adversely. The guys in the family, lucky them, do not.
Not that it means a darned thing for soapmaking obviously, but I'm a chemist.
Oh and yes, you certainly do absorb trans fats from the soap. Also scents, dyes, or anything else.
Were our skins completely impervious to liquids, it sure would make finding a soap we can safely use much easier, but skin is not like a plastic bag, and whatever you put on your skin, you take in internally somewhat.
One of our friends has a deadly peanut allergy. If he as much as touches chicken from Chick-fil-a (cooked in peanut oil), he will stop breathing. Needless to say we don't get near a Chick-fil-a for hours before we go visit him.
Allergies are very serious stuff for those of us who live with them.
For any of the fine soapmakers on here who sell product, if someone asks you, please don't try to tell them the soap is harmless though it has something in there they are allergic to, because that is flat out wrong.