Larger bikes are completely unstable. There is a reason that Zinn builds his custom "project BIG" bikes with headtube extensions, but tries not to let the seat tube get above 58cm, even for a bike that is for someone 6'9" and will be an effective 69cm/70cm bike. They show a lot of seat post, and the head tube extension allows the handlebars to be in a relatively neutral position to the saddle.

If you have a big frame, you can't ride hands free on most of them without veering immediately or death wobble just instantly crashing you. Even on a XXL compact geometry Giant OCR1 I've had shimmying and death wobble so bad on a descent (even with my hands FIRMLY in the drops) that I was terrified I was going to crash. I was really moving, but big bikes are inherently unstable.