Shaggy829
Yes I know most people simply look at the rider weight and not skill level. I also know that some people forget to take into account the rising rate of the linkage and the length of the singarm and the size of the rear wheel. A good example is my 2001 CR250 compared to a 2001 DRZ400, if one person owned both bikes and used the same skill level on both bike and used the CR for MX and the DRZ for two track, back roads and trail rides - the rear spring would still be heavier on the DRZ.
Spring rate is used to hold up the weight of rider and bike as we all know. However, your specific valving and oil flow philosophies (restrict flow with a low flow base valve or increase flow with a high flow base valve) also affect the spring rate to a minor degree. The valve stack can also be used to compensate to some degree for the wrong spring or to achieve a specifically design suspension feel based on rider preference. Mac would HATE Larocco's bike and visa versa.
Next, spring rates based on rider skill level is NO NEW SECRET to suspension tuners. You find a rider who is fast and does all the big jumps but has poor riding skills and never hits the downside of a double and you better give him a heavier spring till he learns to ride. Know find a very fluid rider who always lands on the front wheel or better yet, land equally on both wheel with the bike at the same angle as the down slope and has great timing - know he can run a lighter spring if he prefers. Some of the same concepts go for setting rider/race sag. You can't just do what the numbers say and set all bikes and riders to the same thing.
If it was that easy, then every degreed mechanical engineer who truly understood thermal dynamics, fluids, defection, modulus of elasticity, calculus and mechanics of materials and so on would all use the same base valve and shim combos. Think of it like a engine dyno, the bike with the most or widest horse power on the dyno isn't always the best on the track.
This is just my opinion and we know what opinions are like.