I remember being genuinely disappointed to learn that Andre The Giant was only around six ten or eleven. When Vinnie Mac used to interview him, he would always take his shoes off, or have Andre stand on a box or something.
Maybe some of these guys were measured with and without their shoes. I'm just at 6 foot... but when I put on my shoes I almost 6' 2" tall... It could be the case of just being measured with and without shoes.