Yeah, it mystifies me why this is apparently an issue in some places.
Here on the west coast, all three states would far rather you pull off and nap than nap while you're driving. Six hour limit, which is plenty of time to recover, and I've never run into anyone timing you either. No campfires, no tents. Cooking with your camp stove is fine. Especially in summer, with lots of people on the road, it can sometimes feel a bit like a slumber party with strangers. The traffic can be a bit loud though.
Night before the eclipse, some of the larger rest areas in Oregon were staffed for the night (they usually aren't.) The one where I stayed is also a put-in/take-out for a popular river, and reaches under the overpass to the other side. The attendant said there were several hundred vehicles there. He wasn't there to enforce the time limit either, but to make sure the restrooms were stocked with plenty of TP and that people were parking in an orderly fashion so no one was boxed in.