The reason the N1 (and TQ) are low when doing this is the blades are in autorotation and being driven. The FCU senses this and drops the engine rpm back to a lower amount. TQ will also be on zero ( or a very low amount) because there is no TQ the rotor system is in autorotation.
The guy in the video obviously did not know his machine, and by all accounts is a instructor and flight examiner. It was either a big show or he had no idea at all what was going on, i think the later.
Theres no way i would want to do a check ride with him with his lack of knowledge let alone do a rating with him, imagine the lack of knowledge the student would come away with, it would be dangerous.