Absolutely not, they may well have more than one or none. You are thinking about this like a human you must think like an electrical engineer.
Sorry about the (unfortunately true) EE joke. The multimeter sounds like a good idea but, I doubt you have found all the connectors. When I built my Cobra replica, the kit used an 88-93 Mustang wiring harness. After a serious wire diet I still have 54 circuits going to the dash.
You are really at the point that you need a diagram to help you identify the color coded wires. I did a quick search and found several sites that sell diagram files pretty reasonable. You could also get a detailed list of the circuits served by each fuse (yes I still suspect the fuse box).
Don't worry about engineering jokes. While contorting myself to get to the interior fuses I came to the conclusion that the designer doesn't have kids because if he thought that was the best place to stick a fuse panel he probably screws his wife in the ear.
One last thing that I forgot to mention earlier and I'm not going to worry about it again until tomorrow afternoon.
I had the instrument panel unplugged and out of the dash sitting on the passenger seat. I was just going to lock it up and leave things there. I hit the electronic door lock to lock the doors and nothing happened. If you pressed it to UNLOCK the doors it would work but not to LOCK the doors.
I didn't think much of it. I shut the door and used the key to lock the driver's side. Then attempted to do the same on the passenger side. The passenger side door would not lock with the key. I could turn the key to left or to the right and it was like nothing was happening.
I went back to driver's side. Plugged the panel back in. Locked all the doors. Then re-pulled the panel before shutting the door.
What would the instrumental panel have to do with the electronic door locks and how in the hell could it affect the manual locking of the door?