How do you feel about his claim that this would be good for energy efficiency?
It's unproven. If you have to haul more mass around, that's worse for energy efficiency.
easier human-safety by having the torque (limited)
There are mechanical 'fuses' for torque limiting.[1] Having a transmission that can downshift into a very high torque mode is probably worse for safety. If torque is directly proportional to motor current, there are lots of standard safety devices for limiting motor current.