I don't think that is what he says at all. There are some relative wind directions from the left where the MR vortex can be ingested by the TR and make heading control more difficult but otherwise left crosswind uses less pedal and less power than a right crosswind (US rotor rotation) as all their pedal curve graphs show.
You can get caught out with a wind from the left if it is past the 9 o'clock position as the weathercock effect can push the nose round towards a downwind position - depends on the aircraft and its distribution of lateral surfaces fore and aft of the rotor mast.
The highest percentage of accidents are spinning right (US rotation) but not because of a left crosswind.
I'm not sure what he was getting at with that example, but the way he brought it up just made it seem like he was trying to dispell a myth?
Either way, the left crosswind preference seems more like a high altitude technique (which like lowering the carb heat on short final) just isn't necessary down here at sea level,...but then there are plenty of techniques which are best suited just for specific conditions.