That's probably just their truck being shite, without regular maintenance, and such. As you've pointed out, lots of them don't own their trucks, and "rolling coal" generally refers to the practice of intentionally modifying a diesel truck to shoot out unburnt diesel fuel, usually through a straight pipe, and usually angled to be facing other cars or people they're hazing or whatever, from what I've seen. It's not unlikely that semi truckers, which is a sector that uses a particularly large amount of diesel compared to the normal car having population, would have a percentage of the fleet at any given time which is falling behind on maintenance to try to eek out more profit. Maybe their engines are just running rich, or probably more likely they have clogged air filters. Dunno what would be causing it to get past the catalytic converter and the rest of the exhaust manifold though, and just blow out straight with black smoke. That all seems like it would probably have to be modified intentionally, to see it with any frequency, ja? I dunno, hard to say.

I dunno I also say you've seen it around austin and san antonio, around college campuses, and that checks out to me as a more political kind of phenomenon, then just, say, seeing people running around town and hazing bikers or whatever.

So, I dunno. Does it count as rolling coal if your car is just shite?

have you ever seen a semi do that intentionally to block the vision of other people driving on the road? Or specifically, just to be an antagonistic force of the road?

that video you linked isn't being actively malicious or anything.

If you’ve ever had to drive on a highway full of semis and smell all that gross exhaust, I think you’d feel otherwise. When they’re just belching it deliberately (used to be common place when they passed through Austin, TX and wanted to Own The Campus Leftists) its even worse.

that's kind of just true for all vehicles, the exhaust part at least. I could see that happening in texas though im not gonna lie, texas seems to be full of a bunch of pretty dumb people from time to time. But even then i'm really sure it counts as "rolling coal" as used in common parlance when referring to road rage type incidents. As per the OPs comment.