Question : Do all the power windows work ?
If they do, then I really wouldn't worry about it, maybe the previous owner did have a problem with the original wiring to the rears windows and re-wired them to solve the problem
To my knowledge there wasn't any major issues with the windows.
This is always the problem when you have a vehicle which is 8 years old and had a few owners. When I make changes to wiring, I draw out revised diagrams and put them in the service manual - but then I am a little anal.

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