Many of them may be demos or loaners (Canon put a lot of 7D2 units in pro hands to shoot some major sports events last winter/spring). These might require replacement of the rubber grip surfaces, buttons, etc. depending on how they were handled. Or they might be store displays and never turned on.
I have a 7D and a 5D3 too, and can not treat the three cameras as identical when it comes to setup and use. I transferred the 5D3 settings to my 7D2 and while it worked well for initial testing, I found that it was even better when I experimented with some AF case settings.
Beware that using advanced AF settings before being familiarized with the camera is just asking for trouble. I could just as easily have moved one setting in the wrong direction, and from experience that would have wrecked my keeper rate. Now that I know that detail, I'm in good shape. Someone else's settings may be totally wrong for you, or they might be close enough as a starting point. It's my feeling that while Canon's descriptions of the case settings is technically correct, you still have to understand how they apply to your style before you can confidently make a change and predict the result.
Example: they imply that setting tracking sensitivity higher will allow the camera to track foreground subjects better rather than getting caught on the background. True, but apparently I shoot in conditions where the background is sometimes more contrasty than the subject. Unless I set tracking sensitivity to the lowest, my camera locks on the background far too often. No doubt I'm letting the AF point drift too far away for too long, but regardless, this fixes it. Would this work for someone else? Maybe not. It took me several weeks to find the perfect combination of AF point, case settings and my shooting style.
Ultimately you have to set the camera up for your style, or spend a long time figuring out what it expects and adapting your style to it. I think this is the core problem for some people who jump right in to the case settings and make assumptions. Even though I am quite comfortable with my 5D3, this is not the same camera. There are some differences between AF on them even with the same lens attached.