While I applaud any effort to get people to use less power in their rigs while using less space and case materials- this is asinine- these cases are every bit as big as ATX sized cases so why would anyone want to limit their buying choices in PSU's?
It really does beg the question.
In the case of the Q37 and O10, the height/depth are not much greater than the Mini-ITX/ATX motherboards they house (a little greater vertical space for water cooling) and the width is only increased by the height of an SFX PSU, rather than ATX. In that case, it stays about 2" narrower than an equivalent design with an ATX PSU.
A modern SFX PSU can easily power a modern GPU/CPU combo, so nothing is lost, although it might cost a little more. If you are buying a Lian-Li case, though, I doubt you are worried about cost.
I like the design. If they had somehow incorporated the water-cooling solution into the back-side of the PC-O10 it would have been better. Looking at it there is definitely room, and could have cut off even more vertical height.