give better a good whiskey than reports from the sim :-)
i cannot say how the simulator manages this, but heared that especially turboprops in the microsoft sim are hard to simulate correctly.
nevertheless- going over the gate ( so in true beta) disengages the prop speed governor on ANY pt6.
doing this in a dive is asking for bursting the gearbox by propoverspeed .
the free turbine design pt6a without a automatic spool up to prevent negative torque on the prop shaft and so allowing the prop disc braking - pulled back to full idle- will brake as hell in a dive without the "need" of going into beta due to the described above.
that reflects the impressive dive on a porter and correct reports of your pilot that he goes NOT over the gate inflight.
enjoy !