These seem to be re-treads of the Puma folder, or the Puma was licensed from Slingshot.... can't remember which. The idea is that the bike locking cable is integral to the frame itself..... if you cut the cable, the bike's back is essentially broken and it's no longer usable. Acts as a theft deterrent, assuming the potential thief recognizes how the system works, and isn't interested in merely vandalizing the bike anyway.
I haven't seen any of these out in general use, and haven't ridden one myself. One thing I have noticed, is a fair number of these(the Puma version, that is) in "near-new" condition showing up on Craigslist, which suggests to me that perhaps owners of the bike aren't completely satisfied with either its ride or folding functionality.