Brilliant design and great execution! Love it.
"Sometimes I just wonder whether the people that design things ever actually use them."
I think this is less the issue than the fact that all camper designs are compromises. For instance, these guys probably made a decision that occasionally brushing snow off the walls before breaking it down and getting some water inside was an okay trade-off compared to the disadvantages of other designs such as a soft-side pop-up or a non pop-up. Other people with different camping styles might make other compromises.
I think all small campers have to deal with the fact that moisture, mud, snow, etc. will get inside one way or the other.
It appears that what they built has an amazingly high degree of all-season functionality while also being very compact and light weight.