The reason why vegetable trans fat is called “artificial trans fat” is because it’s not naturally occurring in plants

Artificial trans fats (or trans fatty acids) are created in an industrial process that adds hydrogen to liquid vegetable oils to make them more solid.

You may be right, functionally similar to natural ruminant trans fat

Except that foods containing ruminant trans fat has small amount while processed foods containing partially hydrogenated vegetable oils has a lot more.

Tl;dr: most of the trans fat consumption in the US is from plants not from meat due to high consumption of highly processed foods.

The reason? Crops like soy, corn and canola are highly subsidized and are used in a lot of food processing