Having spent quite a bit of time on the road, it’s usually pretty easy to spot the difference.
That is if you even notice the stealth campers (to your point). But that’s really the original point - most people don’t notice the car dwelling locals, who spend a lot of their time making sure they aren’t noticed.
We have an RV problem so we’ve also gotten good at picking out stealth campers, not that it matter much since I really don’t mind someone who is just sleeping in our neighborhood if they aren’t doing anything crazy.
People sleeping in cars are also common, and pretty easy to spot since unlike a van, it isn’t common to block out all windows in a car. I’m guessing those are all economic cases.
That is if you even notice the stealth campers (to your point). But that’s really the original point - most people don’t notice the car dwelling locals, who spend a lot of their time making sure they aren’t noticed.