AWD/4x4 EV Swap (leaf donor)

As I was searching for cool AWD vehicles I can across this leaf ev swapped Land Cruiser. 
 

He used mostly leaf parts for the build, the interesting thing to me is he didn't use a transmission at all, instead he mated the leaf motor up to the transfer case. 
 

He installed another "black box" gear box in front of the factory Land Cruiser transfer case .

My question is, what if you didn't have the extra black box gear box, and just ran the leaf motor directly to the stock transfer case? 
 

Would it only go 20mph? Would the electric motor "stall out" trying to go up a steep grade? 
 

I don't really understand enough to think though the advantage of adding the black box vs right to the factory transfer case. 

I'd guess it would "stall out" trying to go up a steep grade. An EV motor typically has 3-5x the rev range of an ICE. Typically they have a single gear ratio somewhere around 10:1. With the TC in a 1:1 high range and diffs in the 4:1 ballpark, that's not much gear reduction. With another 4:1 reduction that's around 16:1 which could make sense for lower speed usage with huge offroad tires.