but have to give the points to Nikon on this one, and was expecting a bit more from my 6D. Im just a hobby photographist, but in some cases you can't go back and retake the photos nor have time to compensate for exposure,
But why do you "expect more from the 6D"? The best exposure (of the subject) is the one where you had AF activated and the AF point on your subject, which is what you should be doing when taking shots. The other 3 images are only slightly out and then only because you were deliberately trying to demonstrate the metering difference by moving the point over another tone. Any differences here were surely caused by you realigning the camera, deliberately, to demonstrate the "issue". If you have your focus point on target, then the exposure will be better (when allowing the camera to set it from the meter). Any time you use an auto mode the exposure it sets will change as you move the camera around and it sees different tones. This is true of Canons and Nikons (if a Nikon doesn't alter the meter reading as tones change in the metered area, then the meter isn't working properly). It only takes a second or two to set exposure manually, maybe another few seconds if you want to do a test shot and check the histogram as well, then that exposure will be fixed so long as the light doesn't change. The meter needle will be swinging around though as you move the camera, but you just ignore it.
I agree that sometimes there is a sudden need to grab a shot, with no time to check or adjust anything, but those shots of yours are only a little over one stop between the "correct" one and the worst of the other 3, that is well within the latitude of digital sensors and you can correct for it in processing very easily. You may lose a tiny bit of quality but that is the nature of sudden grab shots, they are rarely taken with perfect settings.
This really is just a matter of getting used to your equipment, all cameras are different and you quickly adjust to the way they work.