I read that in the article. I'd also like to read why a five-speed transmisison is beneficial on these cars - I suppose the motors still have a RPM-based powerband, even if it isn't as drastic as gas engines?
If torque is the same at 5k revs vs 10k (to pick numbers from thin air), when you downgear 10k 2:1, you double the effective torque over 5k at 1:1, for the same output revs.
The battery layout and chemistry will limit the actual power that can be delivered to the powertrain (discharge rate). A faster electric car is not one geared higher, but one which converts the most of this energy into motion.