The English language version of the pilgrim office website also states "You can do the Way in stages, provided they are in chronological and geographical order."
The Spanish version has additional information that makes it even clearer that
@AngelCaido does not qualify for a Compostela when he takes a taxi to switch from the
Camino Frances in Arzua to Caldas de Reis on the Portugues. The distance between Caldas de Reis and Santiago is merely some 40 km, the same as the distance between Arzua and Santiago.
Cuando se emprende la peregrinación, se elige un camino oficial y se peregrina por la misma ruta elegida, sin alternar ni mezclar las rutas de peregrinación.
Meaning that on the last 100 km to Santiago you must stay on the same Camino. You cannot mix and match Caminos on the last 100 km if you want to qualify for a Compostela. You could perhaps win the argument in front of the desks of the Pilgrims Office (and good luck with that!) if you
walked from Arzua to Caldas de Reis but that is some additional 70 km. The Compostela is a recognition for a pilgrimage to Santiago that is walked in a 'normal' way towards Santiago and not in circles or artificial pirouettes.
BTW,
@AngelCaido, it is nice to have a Compostela as a memento for a pilgrimage during a Holy Year but there is no connection whatsoever between Compostelas and Holy Years. Just to clarify in case there is some confusion about those rules, too
. Walk your two days from Arzua, get your Compostela, and join your friends for an additional two days from Caldas de Reis - for the win, as they say
. Buen Camino!