I'll have a guess at this and say its because Portuagal didnt really exist as a nation until 1128. The mod starts about 50 years prior to that

Portugal gained its first de jure independence (as Kingdom of Galicia and Portugal) in 1065 under the rule of Garcia II. Due to feudal power struggles, Portuguese and Galician nobles rebelled. In 1072, the country rejoined León and Castile under Garcia II's brother Alphonso VI of Castile.
Portugal traces its national origin to 24 June 1128 with the Battle of São Mamede. Afonso proclaimed himself first Prince of Portugal and in 1139 the first King of Portugal. By 1143, with the assistance of a representative of the Holy See at the conference of Zamora, Portugal was formally recognized as independent, with the prince recognized as Dux Portucalensis. In 1179, Afonso I was declared, by the Pope, as king. After the Battle of São Mamede, the first capital of Portugal was Guimarães, from which the first king ruled. Later, when Portugal was already officially independent, he ruled from Coimbra.
http://en.wikipedia.org/wiki/History_of_Portugal