There are two routes to chose from when leaving Baamonde, but neither are related to a new alternative route that appears in San Breixo. Both routes from Baamonde are suitable and rejoin just out of town.
Beyond the two options out of town mentioned above, there will soon be another very important deviation when you get to San Breixo. There is a bit of controversy surrounding this option, based mostly on the opposition voiced by business and albergues along the old route. For now there appears to be a bit of an agreement that the old way will remain.
However the new way does exist and it is a full 10km shorter, a distance that tells you just how indirect the old way was. The best and most up to date description of the new way can be gotten from the owners of the KM111 bar in Baamonde.
Essentially this new option begins in A Fonte and bypasses both Miraz AND Sobrado, though there is an option along it to get back to Sobrado if you wish. The two options rejoin in Boimil. This new route is marked, but there are no services along the way.