In all the videos testing electromagnetic fields (EMF) in cars, a common problem is that they either conduct the tests while the vehicle is stationary, or they neglect to assess EMF levels in the rear seats while the car is in motion.
i wonder if the RF radiation is more of a concern, this can be for ICE and EVs, more and more cars seem to have telemetry, for controlling functions of car with apps, for navigation, locating the car, etc, my meter reads high in a van I tested it on.
There are all sorts of EMC fields that device will only be able to detect very high frequency waves. Many electric motors produce very long wave EMC radiation which your device will be unable to detect. This is not an issue health wise however and inside the car extremely low. An aerial to detect these frequencies is several feet in diameter or close to 2m. A bit difficult to handle!