Well I thought the same way you did. So I went and pulled my switch out. Only to pull the switch apart and drop little springs and balls on the floor of my truck. This is the second time I have done this. The first time I got it back together but lost the fog light. I was planing to buy a new switch anyway. So now I had to. By the way it cost $67 dollars. When I finally got it unplug the lights stayed on anyway. So I disconnected the batteries and went to bed.
I found in the morning that by removing the fuse with the special plastic bracket around it the lights would go off. I think it was called IOD. So I went to the dealer and got the new switch put it in and the light still stayed on. Now I am figuring that the CTM is to blame also. So I dis connect the 2 big plugs on the bottom and the light are still on! Now I figure there must be a relay someplace that is stuck on. By this time I just want to finish the install of my new radio and call it good.
I decided to I would just take it to the deal and have them check it out. So I buttoned up everything, and get ready to take it for a ride. By this time it is getting dark. So I have to adjust the dimmer switch again for the dash lights. As I do, I see that the rear dome light turns off leaving the map lights on. So I push each map light once and now they are all off.
Problem solved I guess. I am not sure what to think. Other than maybe this whole thing was computer related, and nothing more. I guess I should buy a Service manual for my next truck, so I don't have to wonder what the wire path to the light are, next time something like this happens to me again. please let us know what you find. It is funny we both had this happen a few days apart. Maybe there was a magnetic shift?