Varying VR1 varies the time period killing two bird with one stone.
The software can use this instead of an internal timer making it separate to the software and this provides analogue control without ADC input.
So this is now showing the single output from the Arduino is amplified to the motor and can control the switching of both IGBTs independently.
This is true 3-state trinary amplification of the PWM inputs just as a classic binary PWM output of a class-D audio amplifier.
More importantly this can never suffer from shoot-through as it has does not have the fourth state of both IGBTs on by design.
Thus eradicating the need for complex shoot-through detection and elimination electronics.