Sorry to hear of the demise of your camera. I know the feeling.
When I started reading your post, I thought I wrote it. :|
"I have a screw loose" :-( g9. Currently in for repair (not w canon serv). The place I found seems quite thorough and exacting... that they go through a strict calibration process after replacing boards. Especially the main board. So I believe you are getting right or correct info as well, though I'm not sure what they could map over from one to another. Maybe that's just a way of saying that to get the camera correctly set-up and tuned, the home DIY'er would need to do it that way (copy over). I think the pros have the equipment to set it up fresh.
I am still waiting due to parts delay, so don't have much more to contribute right now.