This is entirely incorrect. You cannot permanently import or register a vehicle which has not undergone homologation. None of these vehicles have been certified to meet US safety standards and they cannot be imported permanently.
Simple and legal are different matters. There's a BYD parked in my neighborhood pretty often (Central Texas) with Mexico plates. I have no idea how "permanent" it is, and yet there it is.
Your comment is also partially incorrect. Vehicles 25 years and older may be imported and registered regardless of safety standards or emissions.
https://www.help.cbp.gov/s/article/Article-1100?language=en_...