Here’s my fuller take.

I’m going to assume that readers here are at least passibly familiar with the concept of Shared Imaginary Space (yes it’s imaginary not imagined no matter what the revisionists say).

But by far, most gaming takes place in the unshared imaginary space. I generally throw around 80% (because, when in doubt default to the 80/20 rule) but the point is the overwhelming majority of what you experience at the table is stuff that’s never explicitly shared.

For example imagine a chase scene in Shadowrun. The shared bits include the characters and NPCs involved in the chase, and bits of description like “twisting back alleys”, “the heavy rain”, ” the nearly empty streets because this is a part of town pedestrians don’t linger if they can avoid it”. That sort of stuff.

But now think about the movie playing in your head during this scene. If you’re like me, you have a full on bit of cinema playing in your imagination. And if you’re like me, that cinema has a lot more detail then what’s actually been described. Streaks of neon shining in the wet blacktop, a slash of light from some open back door where an overworked ork is slinging garbage into an overflowing dumpster. The smell of greasy fried food as an alleyway gets passed. The splashes of shoes in puddles. Hanging laundry out to be washed in the rain.

All that stuff is going to be in my head…and probably a different collection of specifics will be in your head, but none of that needs to be made explicit until and unless it become pertinent to the story or mechanics.

At that point we all adjust our unshared brain movies to synchronize those parts that have now been shared. This process is smoothest when all of our unshared brain movies are at least compatible with each other.

Its tropes that make them compatible. The more the game / scene relies on mutually understood tropes, the more similar our unshared imaginary spaces will be, and the smoother the game will run.

The less the game relies on mutually understood tropes the more work will be required to synch up our respective brain movies and the more potential for immersion breaking retcons there will be.

I like games that rely heavily on tropes. It allows me to give free reign to my inner cinema without having to worry much that my brain movie is radically different from yours in any way likely to matter.