The first person singular in Lorca's four first major works (P del Cante condo, Canciones, Suites, Romancero gitano) is
minimal in quantity: In many of these works are just not that many 1st person poems.
formulaic or quasi-anonymous. "Oye, hijo mío, el silencio..." The 1st person is there, but the poem is not about that person, or the person has few distinctive qualities.
dramatic / dialogic: the first person is often part of a dialogue
non-autobiogrqphical. There are few details that trace back to a narratively defined, autobiographical subject.
non-psychological. There isn't much psychology, or psychological complexity.
non-salient. For all these reasons, the 1st person singular is not particular salient in this body of work taken as a whole. The poems with a 1st person singular are not particularly more significant or important within this body of work.
Why is this important? An autobiographical approach to the poetry does not depend entirely on the subject position within the poems themselves, but there is certainly nothing that requires us to take this approach. The fact that Lorca wanted to write in a less subjective mode is significant in and of itself.