I have had an answer from the museo address:
As dúas figuras obxecto da súa consulta, as situadas a ambos os lados da porta que leva á Cripta do Pórtico da Gloria, no tramo interno da dobre escaleira, forman parte do proxecto do arquitecto Ginés Martínez quen, nos primeiros anos do século XVII levouno a cabo de acordo co encargo recibido do arcebispo Maximiliano de Austria, quen o trouxo a traballar a Compostela. Representan dous guerreiros que portan candanseu escudo e que, en certo modo, escoltan e enmarcan non só a porta de entrada á chamada Catedral Vella, senón tamén o escudo de armas do propio arcebispo situado sobre a porta.
Son dúas pezas pouco estudadas e tratadas, a pesar da súa destacada localización no conxunto actual do Obradoiro. Foron vistas (como sinalou na súa tese doutoural María Elena Cortés) como posibles referencias ao pasado guerreiro do propio prelado compostelán. Non teñen, polo tanto, identificación concreta nin parecen ser personaxes históricos, máis ben son elementos simbólicos de tipo alegórico no conxunto da escalinata. De feito, non era raro que guerreiros pétreos estiveran situados nos accesos e arranques de escalinatas, como sucedeu, na propia catedral, tempo antes, no caso da Torre do arcebispo Gómez Manrique, no claustro medieval, que tamén estaba flanqueada por dúas figuras de guerreiros con escudos.
GT says:
"The two figures that are the subject of your query, the ones located on either side of the door that leads to the Crypt of the Pórtico da Gloria, in the internal section of the double staircase, are part of the project of the architect Ginés Martínez who, in the early years of the 17th century, took it to done in accordance with the commission received from Archbishop Maximiliano of Austria, who brought him to work in Compostela. They represent two warriors carrying a Canadian shield and which, in a way, escort and frame not only the entrance door to the so-called Old Cathedral, but also the coat of arms of the archbishop himself located above the door.They are two pieces that have been little studied and treated, despite their outstanding location in the current set of the Workshop. They were seen (as María Elena Cortés pointed out in her doctoral thesis) as possible references to the warrior past of the Compostela prelate himself. They do not, therefore, have a specific identification nor do they seem to be historical figures, rather they are symbolic elements of an allegorical type in the staircase as a whole. In fact, it was not uncommon for stone warriors to be located at the entrances and beginnings of staircases, as happened, in the cathedral itself, some time before, in the case of the Tower of Archbishop Gómez Manrique, in the medieval cloister, which was also flanked by two figures of warriors with shields."
I suspect that 'Canadian' might not be the correct translation of 'candanseu'. I have it on good authority that 'candanseu' is a typo for 'cadanseu', and so the translation is: "They represent two warriors who each carry a shield ...