While I have no personal experience, from what I know and read about the 31's, the early colorways eg. USA's, Banned, N-7's, Brazil's, Greys and Shattered Backboard's had a rubber compound that left something to be desired regarding court grip.
According to rumors, Nike changed the chemical compound mid-stream to address concerns. It's been said that later colorways such as Black Cats, ASG, Royals and all lows had the new compound which reportedly improved court grip.
This does mirror actual reports some people have posted so it's indeed possible. Plus I'm certain this is nothing Nike would like to officially publicize. If they did the running change, hats off to them for not letting the issue slide, no pun intended.
Again, this info is "pure rumor" so take it for what's it worth.