Perhaps you should read
this. Note that it refers to a flight envelope least likely to induce mast bumping and Main Rotor stall (well in their opinion anyway - where that opinion originates I have no idea) and also note that your manual refers the limitation to a pilot of less than 200 hours experience with 50 on type and has not completed certain awareness training.
The rest of us who have to operate in that environment (moderate turbulence) for all day every now and then, usually work out how to do it safely as we often have to go slow to shift recalcitrant cattle and surprisingly, land occasionally for a refuel and a pee.
This answer from Soave Pilot would have sufficed.
Because that is the airspeed it is most stable at.
In the meantime should you suddenly encounter moderate turbulence, please don't suddenly lower the collective and or suddenly move the cyclic aft.
Cheers maayte
tet