False blood doping allegations because cross-country skiers use both arms and legs?

I must say I am a little bit surprised over the findings of blood doping among cross-country skiers. Of course there exist fraudsters but I wonder if some high level of hemoglobin  in some ell known skiers blood samples might be explained by such a basic fact like cross-country skiers are the the sportsmen that use both their upper and lower extremities 50/50  intensively so to say, whereas runners use their legs to 95%.  If more muscle mass is used the so called erytropoesis i.e. our bodies own regulation of producing red blood cells migt be more stimulated than if using only the legs. Which might explain extra ordinary high levels among skiers.