The reason for it - elastomeric bearings - i.e. the spherical bearing.
This bearing is multiple steel spherical cups separated by thin layers of rubber material. Not unique to the AS350.
It can bend and twist but not move so much in compression. Distorting the bearing takes some effort. The maximum effort is naturally at maximum pitch i.e. the retreating side and is always there.
In forward flight some of the disk is constantly stalled and even going backwards with regard to flow. Stall creates a shift in centre of lift aft on the blade and creates an additional feedback which is cumulative with speed and loading further outboard on the disk where it matters.
The forces are quite high and affect fatigue life and ultimate strength, I think the weak point is the PCL's which will possibly bend. Hence the HYD system was designed to be not strong enough to let this happen.
As it is at the edge or slightly outside of the certified flight envelope and marginally before RBS it seems to be acceptable.
Dual HYD aircraft in the same family which will not yield to feedback have a load cell (flat spring and microswitch) on one servo which will warn with a LIMIT caption to avoid overloading the control system.
There are warnings and limitations in the RFM. "Forewarned is forearmed" but maybe not communicated readily.
"Grey" 355 style wide chord blades may be more susceptible than the old "Blue" B model blades but even a B model is susceptible.