SASless, it is a cart/horse question on regulation/performance profiles and which comes first. There are lots of risks and hazards in helicopter flying only some of which are addressed by regulation. And those tend to be the quantifiable ones. Easiest is the airline model where the worst that can happen is an engine failure, and so that is then applied to helicopter and the regulators come up with different standards, exposures, etc. Some, like EASA, have more focus on compliance to OEM flight test certification procedures than others. In our Wild West view of confined, the greatest risk is hitting something, in the EASA view or PC1, it is the first engine failing (the second one never fails). So the certification authorities go back to the manufacturers and say "give us the numbers and performance charts, and publish them in the RFM". Now over to sales where performance sells, so the manufacturer uses their test pilots to develop OEM recommended procedures to maximize performance and payload, regardless of the real-world additional risks introduced. Two examples: the back up profile in a true "confined" area where you might actually hit something; some of the PC1 runway takeoffs where the TDP is an altitude instead of an airspeed. When I first flew S76, the PC1 takeoff profile was like a "cobra" maneuver, accelerate to a certain speed, balloon up and level, accelerate some more and then climb - just the thing not to do on a black night in monsoon rain with a new national copilot.
Anyway, a horse beat to death, and there are many on this forum (such as JimL) that can explain it much more clearly than I can. Needless to say, in todays world nobody will risk any SOP other than the OEM provided one, to the point that even where there are obvious flaws operationally, like the original AW139 offshore helideck with the too rapid climb through 20', we will fly a far riskier profile until the OEM can come up with a published revised profile. And yes, in the past we had free rein to make those up and apply them ourselves.