The way I see it, the Taycan is, what, ~480 Wh/mi? And this would be 500 Wh/mi for the hummer. That's not too shabby for an unaerodynamic vehicle with a body designed for an ICE and is made to support a battery that is 18" thick (forgot where I saw that so no citation).* So, while not impressive, it also looks about right for something GM would (eventually) make.
Also, while they are planning on eventually bringing the cell cost to <$100/kWh I haven't seen any mention of the density. That's going to be one heckuva heavy battery pack which isn't going to help cargo capacity. {ed: assuming they match where Tesla used to be for packs[1] that would be ~2150 pounds just for the battery. Ouch!}
* I'm still trying to wrap my head around that one. Will it have no ground clearance or will you need a ladder to get into it?
1)
Tesla Model 3 Battery Cell Has World's Highest Energy Density