So do you actually need a motherboard or host computer for this thing to work?
If so, that seems retarded.
Yes. Well considering you could put 6 of these together (assuming spacing with risers and your mobo supports) that's pretty nice. It allows you to scale well as well. But since these are never shipping, it doesn't matter

Supposedly you can also use the USB connectors, so you don't need to go back to building 2011-style contraptions with motherboards, risers and GPU-shaped devices hovering above.