So with that being said a quick reply to greatexpectations' post:
we did tell people to do it. forcing them to do anything is difficult though, and i think is a potential source of too much drama.
I agree there are arguments against using mean skill (which have to be weighed). But in any case, that is no argument against my alternative proposal. To me it seems pretty obvious that it isn't fair to first tell people to play at least one game in the rules and then let them get away with it if they didn't do it. Not fair because it gives them a potentially large level advantage to not play a single game in cases where they hadn't played for several weeks or even months (variance stays low). So those that have listened to your call for at least one recent game in the rules are at a disadvantage compared to that.
Considering that there were many more people who would have liked to play, in my opinion, it would have been better to announce a little clearer that playing at least one game until Friday evening is a necessary prerequisite to play the tournament and then enforce that.
Alternatively, the variance increase since the last leaderboard listing could have been calculated separately.
Again, this is just a proposal for a (hopefully coming) next time and is not supposed to imply anything for this tournament.