Interesting, I wonder what the technical reasons were for the change. It has gone this way with pretty much every hub motor concept that I've seen so far, either they don't make it of the drawing board, or they end up abandoned at the prototyping stage. The GP had me wondering if someone had actually managed to conquer it but alas that doesn't seem to be the case. It's a neat little car though, reminds of the Daihatsu Copen that I had at some point.
unsprung weight is what every engineer who looks at a hub motor will think. The less of that the better. Engineers would love to move the brakes off the wheel (there are safety reasons not to, but it would make the car handle notably better if you did)
Citroen DS/ID had that, SM as well. CX and XM did not.
Don't even need to be an engineer just go ride some nice bikes, it is an amazing and very tangible lesson in the cost of unsprung weight.