Car derived van is simply down to what was type approved first.
There is at least one van derived car, but I can’t for the life of me remember what it was. It’s subject to van speed limits though. Might just be something obvious like a VW T but registered as a car and paying VED at that rate rather than as a commercial vehicle.
The Berlingo car ….has seats. Iirc it also has a lower pay load due to softer springs.
Other way arround actually, the Multispace gets the stiffer setup.
Although it’s possible that a Berlingo with seats could qualify as a Dual Purpose Vehicle, and thus be subject to the same speed limits as cars.
Dual purpose vehicle was a different thing, that was a tax dodge on company cars if they had a separate load area.
So a Berlingo wouldn’t fit it under any definition.