Update on the issue: the last time they were working on the markers was last Friday, so I thought they'd be stopping for the weekend and continuing today, Monday, in the morning. But they haven't! I went to check, and the markers of the other route have still NOT been removed. Maybe they'll be doing that later on, when they pass again installing the shell tile, kilometric point and painting the arrow in the markers...
Also, they stopped the work right at the Roman bridge, so that the next marker, at the top of the narrow path coming from the bridge up to the road where Albergue Ponte Ferreira is just a few meters further ahead, is again one of the old ones. It could be that the work this time was just to install the markers along the "via romana" leg of the Camino between San Román and Ferreira, and that they will be doing another set of works further on, in a few days/weeks/months.