I think the idea of the mis-aligned wheels is to have 4WD-esque stability without having four actual wheels contacting the ground and causing friction. Basically the corners of the chassis without wheels will scrape along the ground rather than have you roll forward or back when you're trying to go in a straight line, but the small contact area of the two wheels on the floor makes it easier to spin on the spot. Also it means you can lay your drill motors out closer together if that's what you want, as opposed to having them end-to-end. Take all this with a pinch of salt though, I've never built a thwack/flailbot myself.