Interesting question.
This doesn't answer your question, but here's bit of context for comparison with nordic skiing: Northug wins races because he is such a good sprinter and tactician. Even his 50k victory was really decided in last few hundred meters of sprinting. The Norge thug rarely gets beaten in a sprint finish, but he tends to not do nearly as well in time trails or individual start races.
I've seen Norge thug lurk in back in about 30th place for most of marathon races and then move to front in final kilometers and take race in final sprint. When he is on, almost nobody can match his explosive closing speed. You need to beat that guy earlier in race. I'm always surprised, and start yelling at TV, when leaders let him creep up to front near finish. They are signing their death warrant.
Northug a bit like Farah in that regard--not necessarily the fastest in gun-to-tape race but sly tactician with killer closing speed.
As mentioned by previous poster, nordic ski "sprints" are not really comparable to running sprints in track (e.g. 100-200m-400m). Nordic spints are multiple rounds of about 1.5k. So it would be more like running 4x1,500 meters over very hilly cross country course. There is a big aerobic endurance component, not just raw speed. As a result, in skiing you do see top athletes with range from sprints to longest race, the 50k--not only Northug but also Marit Bjorgen, Marcus Hellner, etc.