He quite likely believes that you are wrong, because he has been told otherwise, maybe misled by the company Mangoal uses to design or manufacture their dashcams!
It is possible to record 4K video files from an IMX 335, and the video can have better resolution than when recording 2K video from the same IMX 335, especially if the 2K bitrate is rather low, as is often the case with these cameras. The 4K video must be upscaled from the 2K sensor though, so it does not have more than 2K resolution, just more resolution than the 2K recording. With 2K recordings, when the codec runs out of bitrate, it will tend to throw away resolution first, while if you upscale to 4K, the codec will tend to keep more resolution than it would with the 2K, and throw away temporal or colour accuracy instead.
It will, at most, have half the detail of an A229 Pro at Maximum bitrate, for real 4K resolution, you do need a real 4K image sensor, and the IMX 335 does not have enough pixels, whatever the version or however you use it.