[The Colonel]

We probably need to differentiate between "congruent" and "realistic" - "congruent" being how we account for specific changes in reality based on setting. For example, FTL travel probably isn't "realistic" given what we know about general relativity but, given its presence in a setting, consequences must ensue ... and if those consequences are absent or non-credible, congruence has left the building. Congruence is the basis on which we slap people who claim "a wizard did it because dragons" and may include genre conventions if necessary.

Of course, setting a game in the real world is going to have a greater demand for realism - but even then you will have standards for things like stringency (how hard does the world respond to PCs actions?). As in all things, looking at what you are taking for granted can be enlightening ... and difficult.