First: Seems to me not clear that the engine is running on idle.
Have flown some older BH 06 without rotor brake. If the engine is stopped you can go out because there is nothing do do on the neutral controls while the rotor is slowing down and you have no possibility to do anything in case of a problem. And the heavy rotorsystem of the BH 06 takes a long time to stop.
Second: Leaved the ship lot of times with engines running during Ag ops. Same opinion like Heliringer.
Third: Also today on high mountain ops we leave the engine(s) allways running because it could be difficult to start up again 3000-6000ft higher.
But use your brain!
If we like to discuss Risk Assessment we can find a lot of real problems in the helicopter business.