The way I'm reading the electrical hook up is 3 wires: Main post goes to battery +, terminal 1 spade goes to idiot light, and terminal 2 goes to + post as well. Shouldn't the + post hookups be switched? Either through the ignition, or via a relay that's switched by the ignition? (I'd think the latter).
Sounds right to me. No need to switch it; when the ignition turns off, the engine stops, end of story.