As a cyclist I think you are on point. Like people, cars have body language. It is so telling that I can even tell which cars are at a stop sign in the middle of the night and are waving me through the intersection even though they have the right of way and there's no way I can see into their vehicle (seriously guys, just go if you have the right of way. I don't trust you) as opposed to someone who is just stopped and not paying attention.