It's more subtle than that.
I believe the concept arose from the UK and specifically the Royal Navy.
The RN helicopters that were used for over-the-water, night dipping had an AFCS that would let you roll into a turn using just lateral cyclic, but with the requirement to hold lateral cyclic into the turn to maintain the bank angle. The only way to get the AFCS to maintain the bank angle without lateral displacement and pressure was to trim into the turn - something the pilots were told not to do.
The rationale was as early stated, that if you got vertigo, just let go of the stick, pull power and you would stop going into the drink.
The problem comes in the configuration of the AFCS. Most AFCS will let you roll to a bank angle with only lateral cyclic, but then maintain the bank angle with the cyclic laterally centered, just like a helicopter without an AFCS. In this type of machine, you don't need to hold any displacement or force to maintain a turn, and you don't need to trim into the turn.
Having done a small experiment with some unsuspecting operational pilots on two different types of helicopters - RN Sea King with the hold-cyclic-into-the-turn, and the Chinook with the cyclic is centered when stabilized in the turn - (and having RN pilots fly the Chinook and RAF pilots fly the Sea King), neither one noticed a particular difference in the way the helicopters handled when doing simulated IMC.
The lesson?
Know the AFCS, and don't blindly follow what others give you as advice and ways to do things.
Personally, if I was doing a lot of IFR / IMC, I'd prefer the AFCS that requires lateral displacement / force for a turn. You're not doing continuous turns (typically only 180 degrees of heading change is required), and it is very easy to get the leans in most helicopters.