Folks, don’t place too much reliance on the sim to provide you with definitive answers. It’s merely a computer model which attempts to replicate the real aircraft’s behavior within certain very limited parameters for which there is data. Outside those parameters, sims from different manufacturers or software providers will likely behave quite differently. This is likely why ATSB saw no value in using the sim.
However, using a couple of near identical aircraft to try and replicate the likely configuration of that aircraft from a safe height may have at least provided partial verification of the theory.
At age 67, it’s entirely possible that the health of the pilots knees were “challenged”. He may not have been able to apply sufficient pressure to overcome the force on the rudder to counteract the full left left trim.
Either way, without an FDR, no one will really know.