I agree with previous posters’ caveats about Crossan, but in this case he’s right, and pithy to boot.
To spoil the succinctness of his phrase, though, I’d quibble with “symbolic” as necessarily the best term, since in itself it rather implies that there is a literal, material, truth hiding behind the text. But if an ancient writer did not consider the material realm to be fundamental reality, then they might write literally (if a pagan) that the sky was a goddess (only appearing as air) or, if a Hebrew, that the world is a temple first and foremost, manifesting as the things we see.
In either case, they would be likely to believe at that time that the literal cause of all phenomena was the activity of God or gods, there being no concept of “natural causes” to symbolise. They may even have been right, given how hard it is “literally” to define what “natural” means in its own right, let alone in relationship to God.
So we have to do some real mental adjustment to get inside their mindset at all, and the “symbolic-literal” dipole may not be the most informative.