it is a stability augmentation device
This sort of philosophy has been around for a long time ... for instance on a few of the piston to TP conversions where a variable downspring arrangement produced an SAS outcome typically to address problems with the miss. The usual simple fix for a system U/S was to limit the power (ie thrust) for the miss to keep the normal prop force (cf as well as nacelle added lift) problem under control.
There are reports in the literature dating back to the 40s and 50s on the basics of normal propeller forces.