Yes you have understood it correctly, be prepared for misty windows
The VA kit has covers for the air inlet. So the only way to get fresh air in is through the floorvents as you have figured out.
I will modify mine in the winter to use the original air inlet on the right side and put a valve there so I can select outside air or inside air. Then route that to the VA faninlet with a homemade cover.
I also found a climatecontroller from Waeco, it give you much better control than the neanderthal control VA suuplies. I mean we live in the 21st century so we could expect a higher level of technology from a AC-control.
If you're interested I can get one for you from my AC-guy in Stockholm.
Jan