I'm an atheist all on here know that and most know I'm a minimalist in
biblical research. But in regards to Jesus quoting Jonah. if we assume
the texts are true Jesus quotes the Jonah story saying Jonah was in the
whale's belly three days and three nights
Except the author of Luke said 'the sign of Jonah' was something entirely different (probably because Matthew's claim isn't even consistent with the 'resurrection story', which has Jesus dead for less than 48 hours).
Regarding the 'sign of Jonah', Luke 11:30, 32 says:
For just as Joʹnah became a sign to the Ninʹe·vites, so will the Son of man be to this generation. ... The men of Ninʹe·veh will rise in the judgment with this generation and will condemn it, because they repented at what Joʹnah preached. But look! something more than Joʹnah is here.
So 'the sign of Jonah' according to Luke alludes to Jonah 'preaching to the Ninevites' and nothing at all to do with piscatorial accommodations or reanimated corpses. At least one of the quotes isn't really 'what Jesus said', let alone whether he meant it literally or not. So it's more likely the anecdotes were entirely made up later.
The author of Matthew, with his Jewish audience, was especially interested in taking things from the Old Testament, and framing them as 'prophecies', often without any basis in the OT that it was ever meant to be considered 'prophetic'.