The Bolt looks like it's maybe the size and shape of a Honda Fit. I'm pretty sure Priuses (the regular kind) have quite a bit more interior room than that.
Bolt specs: http://media.chevrolet.com/media/us/en/chevrolet/vehicles/bo...
If you compare your link to the Prius (http://www.toyota.com/prius/features/weights_capacities/1223...), you'll see the Prius has larger dimensions for passengers (for instance, 1st row legroom is 41.6in Bolt, 42.3in Prius; 1st row hip room is 51.6in Bolt, 53.4in Prius), however less overall passenger volume (52.2 + 42.2 = 94.4 cu-ft Bolt, 93.1 cu-ft Prius, unfortunately the Prius doesn't list separate 1st vs 2nd row volume, but I suspect the Prius wins because the Bolt beats it in rear-seat legroom 36.5 vs 33.4, so the Prius is sacrificing rear-seat room), but the Prius has greater cargo capacity by quite a lot: 24.6 cu-ft vs. 16.9. (There's also a special "Two Eco" Prius which has a whopping 27.4 cu-ft cargo volume for some reason.)
Overall these aren't that far apart, but it does seem to me the Prius is a generally larger car, with more cargo space and a more spacious front seat but with crappier rear-seat legroom.
Also, the Prius has a much longer wheelbase (106.3 vs 102.4), and its height is much lower (58.1 vs 62.8). That explains why the Bolt gets similar volume from so much less length: it sits up a lot higher, sorta like a mini-SUV. Also, the Bolt's page even makes note that the EPA has no category for "crossover", so they call it a "small wagon", meaning GM itself would prefer to refer to it as a crossover. The Prius has never been called a crossover; it's clearly a hatchback car.