Starter Relay Control

The installation manual discusses keeping the starter relay isolated from engine ground.

Engaging the starter relays is accomplished as follows:

1) A Switch connecting HIC-B  #4 and #12  signals the EMS to engage the starter.

2) The EMS then engages the Starter Relay via the Starter Relay Connector.

Do I even need to use either of these circuits ... I am using a Vertical Power PPS (Electronic Power Management) to engage the starer. And I plan to use a switch that is isolated from the EMS to engage the starter ... So the starter relay IS isolated from the engine ground.

So my questions are:

a) Does the EMS need to know when the starter is engaged ? (via #1 above)

b) Are there cases where the EMS disables the Starter Relay even though it is requested  via #1 above). i.e. Above a certain RPM ? Below a minimum fuel pressure ?  Why does the EMS want to command the Starter Relay ?