Back in the day I undertook my type rating on a B3+, but since then, I've had the privilege of flying SD, SD2, and now FX2 variants. Intriguingly, they all exhibited similar behavior, at least in terms of hydraulics
Collective Switch Does not de-energize tail rotor load compensator. HYD-TEST Switch on the console does.
On my maiden flight in the FX2, a seasoned instructor, post-shutdown, opted to discharge the Tail Rotor Load Accumulator using the collective switch. This was instead of the standard HYD-TEST Switch located on the console. Initially, I chalked this up as an FX2 peculiarity and didn't dwell on it
However, the following morning, I was taken aback to see the tail-rotor at its maximum deflection. My first thought was that perhaps we hadn't adequately adjusted the pedals back and forth, leading to an overnight drift to max Angle Of Attack. That could have been it; but, upon landing back at base, our engineer highlighted the importance of performing the TLA Discharge post-flight via HYD-TEST switch on the console, not on the collective
Drawing attention to this Service Bulletin
https://ad.easa.europa.eu/blob/EASA_..._2021-0123-E_1 , it's explicitly stated that the pedals' functionality remains unaffected by the collective hyd switch (well, until the accumulators have nothing more to give). The collective switch Given that the co-pilot I was flying with is an astute professional, your observations, coupled with my experience, hint at the possibility of non-compliant AS350s in operation
It's noteworthy that the bulletin encompasses B, BA, B2, B3, and B3e models, emphasizing that they all should exhibit uniform behavior in this context
Overall to cut to the chase, and if I were to sum this all up there is one important takeway
The main concern identified by the bulletin is that certain AS 350 helicopters had wrongly embodied the modification specified in the ASB, which led to a condition where the solenoid of the tail rotor load compensator was de-energized when the “HYD” cut-off switch was activated. This has the potential to lead to a loss of hydraulic power in TR control, potentially resulting in a loss of control of the helicopter
I know this doesn't answer your question directly, but I hope it helps somewhat