I can tell you the motor sounded angrily powerful when its turning.
Sure don't look or sound like a commutator problem to me.
I noticed only when the pinion slowly rotate and you placed the microphone so close that I can hear the rubbing click click click sound.
When it stood still I cannot hear it, example there is no chattering.
If you powered it on and at 50% pwm, pinion not moving and it chatters, then its commutator chattering otherwise IMHO, sounded like loaded motor bearings.
The scope signal looks healthy as far as I can visibly see.
The 50% PWM at full peak voltages, I think is for a purpose to hold/grip the steering wheel in place. Otherwise it's a waste of energy for non gamer like me.
Hey, considering the loudness of the drive vs the clicks [10,000 : 1], I say it's a "acceptable".
Edit: The NETT average voltage during holding should be "ZERO", it would be this remnant voltage that could cause the unnecessary chattering and commutator wearing. For normal turns, the optical feedback signal will make sure the PWM turns the motor.
So Check that the Positive voltage and the Negative Voltage excursion/drive are equal resulting in 50% Nett Zero current and voltage.