I am on PC with a Virpil flight stick with extension, Virpil collective and Thrustmaster Pendular Pedals.
When the S300 first came out I really loved it. Put it on my Top 10 list and tried to help others on the original thread. As far as I remember, there was a pronounced roll (or yaw?) to the right when I pushed the cyclic forward more than about 50%. But as long as I stuck to small and controlled cyclic movements (as one should), I had no issues at all.
Then Nemeth published one or two updates that were supposed to improve handling, but for me did just the opposite. Now I had the strong roll/yaw at maybe 15% stick deflection, which made flying the S300 very unpleasant for me. I was able to compensate by moving the cyclic not just foward, but equally far to the left, but that went against anything that I had memorized flying all the other helicopters in MSFS, e.g. the Asobo Cabri, the Cowansims, Taogs, FlyInsides.
After many hours researching and comparing, I uninstalled the S300 because it was driving me crazy. Nowadays when I want to fly a small trainer, I choose the Cowansim R22 or Asobo Cabri G2, which has improved nicely with SU15.
I watched your video and don’t see the same effects I experienced. No idea why that is the case. But the weather is too nice at the moment to sit inside and spend even more time to solve this mystery.