We have two of those solar ports.
One is on the side of the RV and goes directly to the battery and no where else (which is strange to me). My buddy who also has an AF product has the same setup.
The other is on the roof and its wires dead end behind the solar controller (it has tiny solar panel on the roof that came with the TT)
I think the only way your son is going to know is if he traces the wires or somebody else here has experience with Jayco solar stuff.