Most rotorcraft have power units that are governed to accommodate a variable load at a (fairly) constant engine speed. Simply put, the engine load controls the fuel input to the engine at a given speed, or speed range to be more accurate.
In hovering flight the "thrust" will be a function of engine/transmission torque, and the principle is that the engine governor ensures that sufficient power is delivered to maintain a given pitch setting. This negates the need for the pilot to have to control the "throttle" in addition to the other controls, as was the case on earlier helicopters.
In fixed wing flight it is likely that airspeed will need to be variable, not fixed, so with the propulsion units tilted forward you could vary the speed by adjusting the governor datum via Engine Control Levers.
The complexity of sensing what mode the engine governors need to be in as a function of power unit angle and control input is not trivial, and is probably a software function within the FCS.