"Currently we use an algorithm that advances you based on how hard the kata is compared to your current rank - the harder the kata the faster you advance. The strictly math based algorithm, advances you to the next rank after completing 10 kata of the next rank."

P.S. So it's not just about honor points...
More than that, you can see in the leaders page (ordered by honor desc), that first place has at this moment 223,104 honor and 1 kyu, and the third place have much less - 108,879 honor, but much higher rank - 2 dan!

I believe it's over 9000