I’ve talked with a number of fanboyish sorts through the years whose comments on realism and consistency suggest to me that they wanted, with a deep and abiding passion, to be able to believe that their favorite media properties did, or could (somewhere in an infinite cosmos), really exist. On some level, their enjoyment of the material demanded that possibility of its reality. For scientifically-educated consumers, that usually means demanding scientific plausibility.
This instinct is one reason why books like The Physics of Star Trek — which explains in detail how Paramount’s accreted technobabble is not, in fact, incompatible with modern understandings of physics — are successful. They help bolster the theoretical possibility of genre media.
There’s a certain indifference to metaphor there, as if a narrative that isn’t literally possible is just a lie, and a not particularly competent one.
It reminds me somewhat of the accounts I’ve heard of fiction during classical Islam, when prohibitions against lying demanded that every story be qualified with a formula like “so it is said” or “but Allah alone knows the truth”. The story is then framed as a tale that might be the truth, even if it’s clearly fictional.
It also puts me in mind of the thesis among some science fiction readers that proper science fiction is a blueprint for the future, and any SF book which fails in this mission by contradicting established fact is just useless.
So what’s going on there? I suspect that for at least some advocates for literal realism, the notion of fictional realms as not merely fantasies, but alternate realities, is crucial to their enjoyment. It’s a sort of amplified escapism; they want to believe that there exists another place in spacetime where they might live different, possibly better lives. They may not be able to go there, separated from the fictional realm by centuries of time or by dimensional boundaries separating alternate universes, but the supposed existence of the alternative is comforting. A mere fantasy lacks the same power.
I think it’s akin to preferring to daydream about winning the lottery rather than daydreaming about learning how to throw fireballs — fantasies as hypotheticals, rather than as entertainments.