I think their point is that the van was a much easier storage vessel, with room and penetration power. Getting out of the van and walking 30 feet has miniscule change on the effects of a munition that's blast radius and fallout are so large.

The entire idea of a vest/backpack/portable device would be more so you can get behind enemy lines by say parachute or such. Although there is no point of a parachute as you don't need to cushion your fall, and no need of the person if someone was already letting you leave said flying device.

That's because thats the only way it can work with low power explosives slapped together by some group with limited resources.