Main and enable power in relation to Ignition barrel position

Hi guys, I just wanted to get some clarification on something I am a bit confused about.

In the wiring fundamentals "what needs power and when" section, main power and enable power are mentioned as driver controlled power stages, I am guessing by driver controlled stages the main power would be the accessory position on the ignition barrel and enable power would be the on position? What I am confused about though, is if the ECU is on the accessory circuit, when the engine is cranked over, wouldnt the ECU have its power cut while in the cranking position as that is what happens to accessories while cranking?

A little bit more information on ignition barrel setups and their integration would be really helpful in the fundamentals course, as it is the biggest thing I have been scratching my head about after going through the course and beginning my power supply setup! Cheers

On almost every car, all engine related stuff (ECU, injectors, ignition) only comes on with "ON" position of the key. With a race car you could choose to have the ECU switched by ACC position of key, and 'enable power' switched with ON position. One reason maybe to easily finish data logging after the engine is switched off, or retain laptop connection. But in a race car you may just have stand alone switches to do whatever you want.

Accessories remain powered while cranking, but lights obviously dim due to starter current draw. The ECU is specially designed to survive this event, while lesser digital devices may reboot.