Thought this article might be of interest:-
Dr José Alexandre Ribeiro de Sousa: O Combate do Sabugal no Contexto da 3ª Invasão Francesa: A Natureza Humana no Campo de Batalha
I have only just found it so have not had a chance to have a look through in detail. However the writer of the article justifies it for two reasons. Firstly, the battle has received little interest within Portuguese historiography, apart from its treatment within the limited context of Massena's ultimate retreat beyond the Portuguese frontier. Secondly, the author asserts, focussing on Wellington's statement (I paraphrase) that the battle was one of the most glorious etc ..., that the victory was all the more remarkable given the logistical problems of, and lack of sustenance available to, the two contending armies.