I believe Schubert had many different methods for familiarizing himself with a poem: reading it aloud and silently, always thinking up new ideas about it, first letting various things knock around inside his head, until he finally decides what to do.
Brahms believed that there was no need to publish absolutely everything that Schubert ever wrote.
Rather, I believe that it is very good, if, with the aid of his songs, we can be reminded, among other things, of the social conditions under which Schubert had to work.