I'm betting the original Pilgrims were not as stupid as we modern pilgrims who purposely climb hills instead of keeping to lower contours. Saw several places along the Camino where evidence of old roads were apparent and were obviously much shorter than the crippled snake of a pathway we walked. On the other hand, similar to our "Native American"trails , I would not doubt that the original builders sometimes deviated from the common sense contour because of local demons, trolls, etc. As an engineer , I found the Camino extremely frustrating to walk as it appears to be purposely laid out just to make things harder than necessary . I would guess that you could take any 12 year old kid off a local school bus and he could design a better Camino. Actually my dog could design a more efficient road!
Have to read Michner's Iberia again--believe he states somewhere there is evidence of Santiago being a Roman Legion Cemetery with roads from all over Spain leading to it. .