Were you mostly sampling from live or correspondence games? Or did you get a balanced mix of both? I suspect that there are fairly large subsets of players that mostly play only live or only correspondence. It would be interesting to see if there is a significant difference between those two groups, or if those two cliques even firmly exist.
I’m not too sure what it would say if a statistically significant difference was found. Maybe those two cliques don’t really mix enough (via a third group of players that play both), so any difference could just be due to independent drift.