Following all this with interest, and I'd just like to pick up
Ojuka's point here.
With this printed on the plate there was no (approved) opportunity to start the turn early or late at pilot's discretion
Earlier than the L/R, I agree - you're outside the procedure. But later is surely OK? You used the phrase "could be initiated", and that's the way I teach it. Our helicopters are obviously on the slow side of Cat A (no Cat H in UK) and turning at the L/R would be too soon, so I describe it as marking the point where "you are free to turn a/r for the Final Approach Track".
Any of you experts disagree with that?