Humuhumunukunukuapua'a:Tobin has explained in many posts that one of the things he doesn't like about building donut wings is the need for a 360 degree zipper. So, it is the zipper specifically that he addressed in the Torus design, but I'm pretty sure it's still an outer shell with inner bladder accessible. The lack of zipper makes it easier to more precisely control the shape of the shell and eliminates a potential cranky zipper failure based on what I have read.
I recently asked Tobin about the lack of a zipper on his doubles donut wing, and that's exactly what he said.

Also, just last week I had my DSS singles wing pinched, creating a small hole. It took 30 seconds (+ drying time) to repair the inner bladder with aqua seal.