I agree to this matter, however it's not just about cars but pedestrians too, billboards changing I think it's cool. It kinda breaks the experience in there, just like the fact that in a such modern game you can't see your own reflection. Among all the bugs this is the one that bothers me most tbh (reflections).
I think pedestrians and cars are done similiary, NPC pedestrians differ from NPC placed manually around around map. NPC placed manually by devs won't dissipear, but you turn back and model will change for another.
Density of NPCs is really high on max level, same with cars, and maybe bugs are less visible, but for low density it's more noticeable.
There is a lot of inpact on performance every time V looks in mirror. Could be because of that, or could be because of poor animation of main character? Anyway, would be nice to see those reflection as an option for whose with hi-end PC.
I've seen opinions about way enigine works, there's no mirrors because if something is behind you it's not there (for better performance I guess and, so mirror won't reflect it. It's like with head of V, when you're in FPP it's not there (again because of perfomance). When you move from FPP to TPP (motorbike) I can see bald head first second, because game still processing hair and hat. Mirrors are always in places, where nobody can walk behind your back, walls are close etc.
When you look at it...mirrors are not really needed for TPP games and CPDR done only TPP games, before Cyberpunk, so I guess there's flaw in their engine, thye were not able to fix for Cyberpunk.