Well then why any scoring formula after all ? Should have been a constant score for all sites (10k).
Regarding your "problem", I thought about it too few times. You're right, new comers are at some sort of an immediate disadvantage, yet considering the total score you could achieve on wechall ( > 1.000.000 points), they have loads of alternatives to "remove that disadvantage". And in the end, one way or another, those who solved the levels when sites were up deserve the points, don't they ? It's not their fault they were fortunate to be active in that period