Again, if the helicopter is being "pedalled" round the turn, i.e. not in balanced, banked flight, the rules for balanced, banked flight don't fully apply.
As usual, take the extreme example to illustrate the point.
Imagine a helicopter in straight flight.
The pilot keeps the altitude and applies no bank whilst rapidly pedalling the aircraft round 180 degrees. Just because it's now pointing in the opposite direction doesn't mean to say it's now flying in the opposite direction.
Any turn where the helicopter is yawed with pedal into a turn, to a degree more than that needed for balanced flight, as sometimes happens at low IAS, remaining forward airspeed can be rapidly lost, especially in a gusty wind.
Quite strong "negative" flapback can occur where IAS rapidly decreases through zero and to a negative value. This could pitch the aircraft rapidly nose down to a situation where possibly insufficient aft cyclic control remains to recover, until forward airspeed is regained and positive flapback occurs, naturally bringing the nose up. Negative airspeed over the horizontal stabiliser (now a de-stabiliser) can make this nose-down pitching worse. Close to the ground that could be catastrophic.
I saw 120 to 130 degrees nose down with no airspeed in a Puma HC1 a couple of times, once with at least one hydraulic pump briefly screeching as it cavitated; it's quite enlightening.