Seeing how Mopar started using ECM/PCM controlled charging before everyone else did, I can see a dealer tech putting the blame on the PCM since there isn't a hard and fast test to rule out a bad voltage regulator. Toyota and Honda also use identical Denso alternators.
The PCM could be using PWM to regulate how strong the field/excitement current within the alternator and the bench test isn't looking at how the alt behaves under PCM control.
The PCM could be using PWM to regulate how strong the field/excitement current within the alternator and the bench test isn't looking at how the alt behaves under PCM control.