What I mean is that in MSFS turboprops, when you pull the throttle past the gate to below flight idle, they seem to all instantly go into low reverse prop pitch and quickly come to halt and even start inching backwards. This seems to apply to all of them including the high fidelity third party ones, with apparently no tools to address or work around it in the SDK. To my understanding what should instead happen is that below the flight idle there should be a beta range of low positive pitch before the propeller finally switches to reverse thrust proper.
This is a taxiing/runway roll issue, since no turboprop is supposed to go below the flight idle during flight. Those turboprops (Porter) that are exceptionally certified to use beta for beta descent in flight have some limited beta range on the flight side of the throttle. (Though in practice the beta descent is not modelled on the Asobo Porter, the Milviz one can do it though probably due to some kind of workaround)
For the requested source, I found this post from SWS (Kodiak) developer: