In my six-years experience volunteering at the Pilgrim Office, I believe Kathar!na is correct. All the other (lesser) Camino routes are subsumed into one of the listed major primary routes.
For example, the Camino Aragones is not listed because it is merely a feeder route into the
Camino Frances. When one comes this way, they spend way, far more time and distance on the Frances than the Aragones. So it is thus counted.
This feeder or tributary relationship also explains why most all the lesser routes are not listed as 'official routes." Personally, I think this is a mistake that needs to be addressed.
All the listed routes have one thing in common, they terminate at the Cathedral in Santiago (sort of). That could explain why the 'official' list is far shorter than the several dozen we all know are out there.
OTOH, the Camino Sanabres is actually the common terminating Camino route segment for the:
- Camino Invierno
- Camino de la Plata
- Camino do Este
- Camino Portuguese Interior, and the
- Camino Torres
So, and using the 'ending at Santiago' logic, the de la Plata, Norte, Invierno and Primitivo ought not be on the list as one must join another route before arriving at Santiago.
Listed above in the 'official' list are routes that actually flow into and enter Santiago on another route.
- Invierno via the Sanabres
- Primitivo via the Frances
- de la Plata via the Sanabres or the Frances
- del Norte via the Frances
In this relationship, it is the main catchment route, ending in Santiago for these known routes.
This said, I recall that the answer lies in the understanding of on which primary "official" route did the pilgrim spend most of their time. So, if you walked the Norte, De la Plata, Invierno, Primitivo, etc. you spent far more time and distance on that primary, more historical, or major route than you did on the smaller segment of the ending route into Santiago. That is why you are credited with walking only on the primary or official route.
The outlier here IMHO is the Sanabres. While not one of the 'official' main routes, I am aware that there is a surge in pilgrims choosing to walk from Ourense. It is emerging as yet another 'just long enough' to qualify for a Compostela starting point, akin, to Sarria and Tui. But Ourense is on the Sanabres route.
In closing, I shall put this on my 'to do' list for this season's volunteer stint. But, if any of you out there are volunteering before I arrive in July, please DO print this out and show it to someone in charge, or in the know. I believe they SHOULD start tracking the route your started on and the route you finished on.
We need to find a way to bring the Invierno and Sanabres out into the open and be counted more accurately.
Hope this helps.