It definitely feels like the Jedi Texts are a patchwork of various authors, of whom Luke is the latest. Certain parts may have survived from the beginning with scraps of ancient papyrus or something, but more likely these are copies of copies of copies, with annotations from a thousand generations of Jedi thrown in for good measure.
This is what I always thought of the Sacred Jedi Texts being. Kind of like that one Jedi Path book. Or “The Red Book of Westmarch”… lol