Paris votes to crack down on SUVs | Non-Parisians will be charged almost $20 per hour to park large gas or hybrid vehicles within the city center in a bid to address pedestrian safety and air pollu…::Parisians have voted to increase parking charges for out-of-town SUV drivers as part of the city’s efforts to address road safety, air pollution, and climate change.
I think it is a given that you can create scenarios for every law that make the law look stupid.
I doubt that the amount of 9 seater cars with enough people inside is actually significant to recalculate the law.
The decision by weight is most likely done as this is a value which can be easily evaluated.