wrong information !
The caminho Português INTERIOR goes from Farminhão nearby Coimbra via the east side of Portugal -Viseu-Chaves to Ourense -and via a part of the Via da Plata to Santiago !
The one you mean is called the CENTRAL route of the caminho Português .
If you read the subforums here you'll see that there is a subforum for the INTERIOR .
I agree with you about the first stage but.. If you take the metro from Porto to Fórum Maia and walk from there , it is a nice rural walk and at the end the nice albergue in Vairão ,O Mosteiro do Vairão .From Vairão is an easy and relaxed walk to São Pedro de Rates from where you follow the CENTRAL route to Barcelos, Vitorino de Piaēs( famous privat albergue Casa Fernanda) Ponte de Lima, Rubiaēs and Valença do Minho etc to Santiago de Compostela.