If you look through the video closely you can see one end has mesh panels. That sounds good to me or you could leave the ends open.
I have also considered making the top shorter than the pole for ventilation, but I guess you could just slide the side up too.
Yes I am also thinking completely closed there would be a lot of condensation. Definitely would need a couple of top vents
From doing a preliminary layout in cad, what is interesting is if the plan layout is 2 equilateral triangles, the fabric panel for each side is exactly 1/4 of a circle.
Sew together 2 1/8 pie pieces x 2 then lay them on top of each other and sew away.
With no zipper seems like a really easy build.
I had considered just putting the pole underneath, but kind of like the sleeve they created and the pole would wear on that and not the body.