Thanks for this link, Anna Marie. Well, this is interesting and confusing at the same time. Pinor is not where I had the problem, it was a few kms earlier, in Coutela/Cotela.
This may be way too much information, but for those who want to take the unofficial detour to the monastery at Oseira, you should do it directly from Cea, not from Pinor. The official Vdlp goes from Cea to Coutela to Pinor, and then on directly to Castro Dozon. (google maps show this pretty clearly, it's along the old Ourense highway 400). If you wait to Pinor to take the turn-off to Oseira, you will have gone some kms out of your way and then will be on a road all the way to Oseira.
From Cea, there is a walking alternative clearly marked for the monastery. I was on it, and it was all through undeveloped land on dirt paths. It more or less went straight north from Cea. At some point on that path, there was an arrow turning us off the path and to the left. This arrow took us right into the town of Coutela and from there it was all highway walking to the monastery (google maps shows this as the Antigua Carretera OU-343, or the "old highway OU-343.") There is a casa rural or albergue of some sort in Coutela, and residents told us the owners were the ones who painted the arrow.
So, if you make it all the way to Pinor, it's nice to know you'll see a branching of the alternatives, but my recommendation would be to head towards the monastery directly from Cea and never go to Coutela or Pinor. And if that deceitful arrow is still there, a few kms after leaving Cea, just don't turn left! Laurie