Connecting Orion to alternator

Hi,
Can i wire my Orion input directly to the switch pin that has an alternator cable connected too, or i have to go directly to the starter battery (dashed red line in the picture)?

I don’t see a reason why the direct connection to the battery is different than on the switch pin and why people are telling me it should be done that way. Aren’t those 2 connection points the same if my switch is “ON” ?

Thank you