I think the Testimonium in Rome is a fairly direct attempt to follow the lead of the Caminos and the Compostela. Even the conditions are effectively the same - walk the final 100km and produce a stamped credencial as evidence. The Via Francigena was not really re-established as a walking route until the late 1990s and until the past 10 years or so numbers walking the route have been tiny by Santiago standards. The same is true for the various Olavsleden routes in Norway and Sweden which are recent developments and where the conditions for receiving the Olavsbrevet are much the same. The vast majority of pilgrims to Rome arrive by plane, bus or train. Those of us who turn up on foot are the peculiar exceptions!
No doubt... but I don't think it changes the point I was making. Dates and popularity of certifications, as well as their putative necessity seems to shift over time.
But the "grand tour" is not new... indeed, was the herald of a 'properly educated' member of more privileged classes going back at least to the 16th Century as *established". To become established requires that it had some feasibility and popularity prior to its being an established thing. That is: prior to making significant enough an impact to enter the official record, people are usually creating and "doing culture".
And yes, a significant piece of my point is that arriving to most shrines happens by the easiest conveyance mode possible. "On foot" -- as I noted in my post -- even for Santiago might be on the feet of the animal carrying the pilgrim...
I have little patience for the modern imposition of "walking meditation" onto the way of St. James (or any other). Yes, walking a pilgrimage route can be health restoring, but walking the whole distance and *refusing* to visit the pilgrimage site (as happens often enough), or casting the site(s) as "Disneyland for Catholics" (graffiti on a wall in Santiago approaching the stairs down to the Plaza Obradoiro, and a refrain I've encountered often enough in casual conversation) seems to miss that *the destination* is the point. For me, a lapsed Catholic, it took three arrivals in Santiago to meet the destination. Timing... catastrophe... distraction... but on the third arrival, I made it to the destination. To get *there* changed everything for me, and a certificate from the office cannot speak to that (though I do display some of them quite proudly, especially the 2 Vicarie Pro compostelas.
Where I think the certification matter comes in with Santiago has to do with the use of the routes as a sometime ejection method for punishing criminals. But there is a historical record to indicate that one could not head out on the road without some sort of permission (from one's parish priest, from a magistrate).
The matter of certificates in their modern/present iteration really confuses purposes, IMHO. And I find the idea of a certificate for walking to Fatima to be.... mmmmm.... *troubling*. How one arrives there, building an economy of tourism along the way... that does not bother me. I think that's great. Follow the blue arrows! But turning the arrival into a quest for a completion document does seem to miss the point of the sacred nature of visiting *the shrine*.