As far as the engine and airframe are concerned, the strain on the rotor head is the same, is it not?
Why do you think it
is? The only sure way is to ask the manufacturer, to see if such tests have been done. They set the operating limits for their aircraft. Once you go outside those limits, you're a test pilot.
Note that test aircraft are wired for data logging using strain gauges etc, and are far more deeply examined than yours is, after every flight.
The real answer is, they possibly have, in the past, explored a wider performance envelope. If they could safely certify a wider performance envelope, they would do so because it makes commercial sense to do so.
But they haven't, so go figure why not.
Would you treat your car like this? Routinely exceed the rev limits, for example, just because you can get it to rev higher than the red line?
I still think you're not for real.