That scale and people vary.
That scale is a huge bell curve and slightly considers build which can be small, medium and large for simplicity.
I was on the low end of large bone structure using wrist and shoulder measurements.
Someone on the low end of small with the same height will be lighter but doesn't mean better-less bone or muscle fibre type-everyone is different.
If you're talking Xc then you post a new thread on the ideal physique of a roadie or mtb bike and the muscle fibre/training type etc.
But looking at the atheletes doing well in their sport like Wiggo we have idea of where to be to win.
Where to be on a fun ride-bugger all just turn up with a beer gut :O)