Again this only being my guess here and not based on anything, i think its just going to be their way of combating people making these modded cars in the 1st place, and then bringing them over. Or as i said, keeping an eye on your stats vs cars/mods ect. Payday 2 has a similar system on pc. If you are a low level and are clearly running stuff that you shouldnt have been able to unlock yet, or if you level up ridiculously fast, in less time then they believe anyone could, then you will be labled a cheater both in game and on your steam profile.
Starbreeze dont "ban" people, but mark them as a cheater if they see progress that would be impossible given your time playing. So say your a low rank, dont have many hours or miles driven, and PD sees that you somehow have so and so car fullu modded, their system will detect this and do whatever they plan on doing. Marking the player as a cheater in their in game profile, banning them from online lobbies/public lobbies/esport lobbies whatever, marking them as cheaters in public lobbies, whatever their system is to punish said cheater.
Not saying this is why, but my guess is as good as any i suppose.