I'm not sure I agree with your experience about uniform wet snow having better braking than "rutted" snow.
If you can position your mains in the ruts, in theory you have less snow between the rubber and the asphalt, perhaps even just water.
But I have never seen any tower differentiate between uniform and rutted snow.
I think for performance calculations it's best to just consider an average depth of wet snow and go from there. No doubt there will be a decrement. This is where experience and good judgment come into play.