smooth stepper to C25R5 BOB and motor controlers

Hello all,

I am working on collecting up all the parts and pieces I need to put together the electronics package for a highly upgraded xcarve machine (screw drive reinforced rails, etc).

I am having a hard time understanding why in the vendor wiring diagram they have the 5 volt power supply going to both the bob and the motor controller?

I am looking to put in a secondary more robust opto or digital isolator but with that extra 5 volt line going to the motor controller it leaves an additional power back flow path to the bob and ultimatly to the very expensive smooth stepper.

I am not sure I fully trust the motor controller since the main power supplies are high as they are turning large motors. Could I just use a separate 5 volt power supply for the bob and then a digital isolator for the pink data feed lines? The nice thing is that analog devices claims that a digital isolator does not need additional power.