Nah - you're not crazy - just pedantic. (I was quoting words from a song!)
1) The Codex need'nt have been based on personal experience and even if it was the work of a bunch of students (as some historians suspect due to the poor Latin) they couldn't have dreamed up the routes to Spain without information based on some kind of empirical reasearch on the roads, distances between shrines etc.
2) A few years ago I walked the "Wainwright's Coast to Coast" in England. We followed Alfred's route religiously, east to west, stayed in the same villages (in some cases the same B&B's) because we wanted to walk the 'authentic" C2C. As you know people are trying to follow Sigerics route from Rome to Canterbury - almost 1 200 years after he wrote his diary.
3) I think there might have been established routes that people would have used, mostly for safety reasons, rather than find out of the way or isolated trails. (There couldn't have been that many options between towns.)
I don't think people were very different to us a thousand years ago. If bishop Gotescalco travelled to Santiago he must have been a celebrity in his town and must have told hundreds of his kinsman about his trek. I wouldn't be surprised if those who followed tried to stick to the same route and visit the same monasteries and shrines. Today, people want to walk the 'authentic'
Camino Frances, or the classic Jomosom trek to Muktinah, or the historical 88 temple pilgrimage on Shikoku. They rarely invent their own routes.
4) So - the bishop could have walked a similar route to the present day
Camino Frances - on the way back to Le Puy.
We can never know for sure.
Thanks for the websites - very interesting.