You're thinking way too hard. The number of wires on the battery terminals has nothing to do with it. Wires split, terminate, and feed other wires all over the place. When those wires hit your power distribution board in your camper there's probably at least 10 different circuits hooked on there.
There really is no danger of having 2 charging sources. You could have: truck alternator, camper charger, solar panel charger, portable charger, etc. all connected and it would all work fine. Some people even do this from time to time.
It's all 12 volt (nominal) so nothing can burn out anything else. All the chargers sense voltage and the voltage will be basically the same.
I actually leave my truck and camper hooked up when I'm camped so the camper charger will keep the truck battery topped off. I typically start the truck to move off the leveling blocks and let it idle while I put things away. I unplug the shore cord last so the fridge doesn't switch to LP any sooner than necessary. I typically have truck running and camper charging every time I go camping.
