Personally, I have a problem spitting hairs like this. Why not do what 99.99 percent of pilgrims do, and just walk from Sarria? It is only about 18 additional kilometers.
Yes, the official rule says you must walk AT LEAST the final 100 km in any recognized route into Santiago. Yes, you can finagle, finesse, and cut proverbial corners to walk not one meter more than you must to qualify.
Each person walks their own Camino, and no one, including me has the right or standing to challenge how you accomplish YOUR Camino. I am, nonetheless, uncomfortable with “armchair lawyering” just to get a piece of paper, that evidently is not that important to you.
Let’s face it, if you put that much effort into shaving this thing to the absolute minimum required, perhaps you should avoid having to stand in a waiting queue for 2 hours plus to get this document, which acknowledges your difficult and arduous journey to come to the tomb of the Apostle Saint James to venerate his relics. You would be performing a service to other pilgrims by NOT queuing for a Compostela.
We do offer a “solo sello” conclusion for pilgrims who only want evidence that they made it to the Pilgtim Office, and not wanting a Compostela. All you have to do to obtain this stamp is to tell the security fellow at the front door that “yo quiero solo sello.” (I only want a sello.)
Many repeat pilgrims do exactly this, instead of seeking the piece of paper. Even pilgrims who have walked very long distances many times frequently opt to simply get the stamp to close out their credencial. They know in their heart that they earned the Compostela, and to not need another piece of paper.
Requesting “solo sello” is immediate and avoids further wasting your clearly valuable time waiting in the line for hours with pilgrims who may have walked 600, 800, 1,000 kilometers or more to qualify for that piece of paper. They will have justifiably earned it. I cannot say whether you will have.