I see your point and it's one that's been discussed over there years. MPH value is chosen due in part to the majority of participants have been from the states. Also, for none participants (again in the states) it allows some ability to relate. Kites, regardless of geographic region are measured universally in meters. And wind speeds, given the relative diverse measurements available, most can relate to knots.
In light of your dissaproval about mph being "so American", I'm no more concerned about measurements in MPH than I am that the ranking is in English. Maybe we will change units. But for now, baby steps.
Agreed that it is difficult to quantify kite speed in relation to wind speed in light winds. But if you can more 12-15mph in wind so light you cannot feel it on your face or even get a reading on a meter then how many times the windspeed have you gone?
The entire concept of what is possible in light wind on a super low resistance surface has gone out the window the last couple of years with the advent of all these new super efficient race kites. The ability to build apparent wind in near nothing changes everything. I now ride and have great sessions on days that we used to think we're impossible to even fly a kite. 3x the windspeed is easy now. And if you have excellent light wind flying skills and the right kite, almost anything is possible it seems.
Riding ice is IMO the snowkite equivalent tinfoil boarding on water. 5 years ago, the speeds achieved in light winds on water today would have been considered impossible. The same technology benefits a rider on ice. Taking it a step further though, elements such as carve radius, snow/ice crystal structure, surface moisture, air/snow temp, base structure and wax selection all play a part. It's not as simple as windspeed, surface conditions and kite size. Just because you cannot achieve something does not mean it's unachievable.
As I said, the GSR isn't about simply being the fastest. It's a means to guage yourself have fun (or sometimes get frustrated) and just see how you can push your personal limits or see how you fair against others. It's also great to see where people are riding in other parts of the world.