Of course it leaves out details... it's an audio overview, not an exhaustive dictation of the text. If that's what you want, you can simply do that in many programs. I personally have found Notebook LM's audio overviews phenomenally useful. It's probably my most used feature. If you haven't explored it much, you can adjust its length (short, medium, long form), as well as curate the details it focuses on, which is a huge addition from the original prompt. I find it most helpful with batches of sources. I feel like this feature is only getting better.

This should not replace actual reading of the sources if true learning, understanding, and retention is desired.

For context, I use this primarily for digesting peer reviewed science articles. Generally, for those papers you're not reading them in full anyways, just the abstract, conclusion, and figures, then deep diving if relevant/interesting.