Reminds me of a friend who bought a Rolex - genuine article etc. However, had a problem and sent it for repair. Some good while after the repair, he took the watch into a local Rolex dealer. When it was opened up it was found to have timex works inside. The Rolex oyster movement had been removed!!
So - are you sure you have a Canon - or has someone swapped out the guts................
Maybe it's because the camera is quite new, and the sofware you are using to read the exif data has not got your model in it's database, so it thinks it must be a Nikon?....