Don't know why the dealership/salesman would tell you that. We have had the Splendide Combo unit and now have the Splendide Ariston Stackable unit and they both were vented to the outside. It is very tight fit, but ours works fine. I wouldn't have a unit that wasn't vented to the outside, the moisture, heat to the inside of the 5th wheel, I don't think you would like that. Both of our Splendide's were installed by Camping World and worked fine. Good Luck...GBY..
We have a Cambridge and I think the Big Sky have the same closet space. Check our web site and see the Splendide Aristion...
www.webspawner.com/users/lnhdch