So John's sexuality is completely sublimated into his skating and/or this is the longest courtship dance ever observed in the wild.

I know you're kidding, but that's an interesting point. John evades relationships as too much trouble (and a distraction) and he doesn't like one night stands -- not that comfortable with strangers in his bed. So that means he always ends up sleeping with friends. If the friend starts to cling too tight afterward, he gets Sheppard-dumped: it's amazing how quickly John can become unavailable.