A vehicle can only SAFELY carry so much weight. Government has legal restrictions on this as well.
Full size vans usually have different models with different load capacities but same body style/shape, with higher capacities being more expensive. Mini vans, afaik, don't offer many gross vehicle weight options.
So when people are talking about full size vans, and Nomading, people are assuming that they're getting the bigger van to haul more stuff. And as we're on "cheap" rv living site, where getting the most out of the least is a trend, those in the know recommend to NOT go cheap in this area if possible.
It's easy to overload a vehicle with lots of space figuring that if it moves down the road ok that they're good to go. Which may be true if there are no variations in conditions, which, usually, is false for lots of us encounter all types of more extreme/different situations than just putting down the road. Mountain inclines/declines and curves, extreme weather conditions, rough roads, emergency braking situations and so forth will bring out the worst in a overloaded vehicle making it unsafe for passengers and/or others on the road.
As much of a noob as I am I've already had situations where I was glad I had more capacity than the weight I was carrying.