Mr. Boutry, chief testpilot at Eurocopter France, is flying this demo and he is as far as I know the only person performing this manoeuvre in the NH90 (sofar).
I am pretty sure the G-forces at the bottom are not the most difficult part of this manoeuvre, and this aircraft is one of the prototypes (instrumented aircraft) with a G-meter in the cockpit.
I admit that together with everybody else I was also impressed with the manoeuvre when I saw it for the first time.