Understanding the generator wiring

Hey guys , so ive been doing some upgrades to the electrical system of my eagle cap 811 , im in the process of installing a victron multiplus inverter charger

As i learn more about the camper wiring and 12v electrical in general , i contacted eagle cap to ask them what the source was of two particular wires. They told me these two wires were actually coming from the generator

Ive attached a photo of these two wires , and a wiring schematic from eagle cap for reference ,

Shore power / generator power runs through a transfer switch and then to the ac panel

But , these two wires are not actually on the diagram (likely because its just an optional add on)

Here's what's confusing me

These wires from the generator were actually previous wired directly onto the battery (I've since moved them to pos/neg busbars

Apparently these wires turn ON the generator by way of the 12v switch located in my control panel section so to speak , its just the simple Onan start / stop switch to turn on the gen

So how does this work exactly ? The switch turns on the generator , but why do we need two 4awg wires running from the battery to the generator ?

the power from the gen should be going from the gen to the transfer switch to the ac panel