The PWM signal is filtered and biased before being sent to the IN- pin of the op-amp. So it is just a control voltage, but without an MCU it would be difficult to change that control voltage, so swapping sense resistors is just easier. Schematic is posted over here.
I also have the H2-C driver schematic, and a similar MCU bypass could be done with that, but you’d either have to run the emitter in 12V mode, or you have to swap around the FB resistors for the MP3428 to drop the output voltage. H1-A is the superior driver anyway IMO. The addition of reverse input protection MOSFETs on H2-C thermally insulates the ground planes from the ground ring, which means the driver can’t dump heat to the host as easily.