It's not that strange. I'm 6' 1" and I fit best on the smallest of 56cm frames, (frames with with a true 56cm stack height).

Something that a lot of people overlook is, if the distance from the top of your shoulders up is disproportionately long, that can mean that the rest of your body (for practical purposes related to bike fit) may be similar to the proportion of a person say, 2-3" shorter.