Of course you may still lift "overweight" and not have any "Adverse Factors", for example use a technique that gets you airborne without exceeding the engine limitations. (for example a cusion creep at sea level on a cold, windy day in an open space and a very shallow climb out). Also consider this, even if you lift at the MGTOW, you can still simulate being over weight by climbing too quickly. ie rotor head pulls max weight upwards,(within limits) which dynamically adds weight during the climb.
So it makes me wonder, lift at MGTOW, climb out steeply within engine limitations, is probably a similar airframe stress to lifting at over MGTOW and make a lesser best rate of climb within engine limitations.