This already happens, vehicles are classified differently due to differing tax calculations and differing driving licence requirements.

I know this happens for tiny cars with tiny motors that don’t require any driving license, for motorbikes which have less wheels than a car, for trucks based on curb weight or for buses based on occupancy. But a SUV and a van require the same driving license (B), have similar size (big SUVs and medium vans are pretty much the same length), similar weight, same occupancy, similar engines. How are they classified differently?