I'd check that inseam measurement if I were you. I am 6'3", do not have long legs for my height and have a 35" inseam, so 36" at 6'6" seems as if it might be short. A cyclists inseam is measured crotch to floor, wearing shoes, not the trouser inseam. Is your friend aware of that?
Anyway, if the measurement is correct he'll have a long torso, so don't worry about the long top tube. My own bikes range from a 58cm frame to a 61cm - their geometries, and my riding position, vary but they all fit. I'd be surprised if you couldn't make a 62 cm fit him, but it's extremely dangerous to give bike fitting advice over the internet. People's proportions, and their suppleness, vary too much to size bikes on inseam measurement alone.