The relevant part is this
Input and output negatives are linked together and go to both the trailer plug and the chassis. This is ok. A bit of a waste to use an isolated Orion to then connect both negatives together, but works either way.
The input positive comes from the trailer plug, thats also correct.
But what i dont understand is the output positive. Why does that go back to the trailer plug, that voltage has no business going back to the plug.
Where exactly do you measure 2A? On the 8AWG red wire thats leaving the screenshot on the left side? If so, then i guess those 2A are going towards the trailer plug. If the schematic is correct, then they could power the brake lights if the breakaway switch is closed. Apparently theres breakaway switches that come with their own battery, so i guess it could be powering that, and as soon as the power is cut the breakaway system goes into standby?