There are flaws in the software. To varying degrees on the different helicopter addons. It’s not black and white to describe which ones are realistic and which ones aren’t. Is more of a scale and different models sit at different positions on the scale. They all do some things better or worse than others as compared to real helicopters. Not only from addon to addon, but sim to sim. There isn’t a simulator available that is a perfect representation of real helicopter flight. The 3 main consumer sims, MSFS, DCS and XPlane are all pretty reasonable simulations for about 90% of the flight envelope when controlling them with realistic inputs…but again, I stress this, none of them replicate everything perfectly.
As for the S300, I posted a video demonstrating what I’m talking about above in another thread. I recreated the control twist responses as you were describing, but then flew it around realistically without any problems making control inputs the way I would IRL.