Dunno about KEH testing for left focus, I doubt they are that tech savvy. As to why people sell cameras, there are a lot of well off folks who buy and sell constantly. They show up at the camera store and ask why this or that happens, and lo and behold they are shooting a $3000 camera on "Program" setting at jpegs, and have no clue about WTH they are doing. I know a few of these folks, usually retired with a lot of internet time under their belts, which makes them want the latest and greatest. I am selling a D800, but keeping my D800E, find I don't need a backup.