Why not just use a normal belt and some way of tensioning it like every other belt drive in the world uses? Seems like the fancy belt (and more importantly, the fancy pulleys that go with it) drives up cost substantially.
Look up-thread. You have to thread the belt through the frame. You either need a special frame with a gap in it, or a belt that can be split.
I read that part. That doesn't explain why they chose that oddball cogged belt instead of a commonly available belt profile (cogged or otherwise) for which pulleys are available off the shelf (or cheaply built to order) and belts are dirt cheap.