Crab.....have you ever heard of the US Army and other US Military forces?
They do operate helicopters and train their own pilots and have done so for quite a while now.
You might read up on its training system and how it came to be.
Even Bristow Helicopters trained their own Cadets without using airplanes....and they did so too far beyond PPL level as you well know.
Those Students started in the 47 or Robbie and ultimately found themselves as Captains on 61's, Super Pumas, or 225's.
The RAF is but one organization that teaches helicopter flying and does not have the unique path to salvation in that enterprise.
Exactly why does being assessed on a simple machine to master equate to a proper assessment on one that is more difficult?
It is not unheard of for a Student to go Solo on a helicopter in under Ten Hours.....not much more than for the same in an airplane.
So what is the quantum leap between an airplane and a helicopter that demands learning to fly an airplane should be done first before venturing into learning to fly a helicopter?
Now when it comes to something like a V-22 Osprey or the 609 (if it ever reaches production). there might be a benefit if one is to be pipelined into that type aircraft.