That's the way the pro's do it. It doesn't seem to load up enough to bother the working stuff, but I agree it seems like un-good engineering. Another thing, the vents invite wasps and others attracted to nooks and crannies and propane's smell to build in there. I always inserted some metal screen material behind the vent, cutting it to full size and letting friction hold it in place.
Better in a Class B style van would be the Engle type chest refrigerator that needs no outside venting and, in practice for me, doesn't add much in the way of extra heat inside.