It looks like you're new here. If you want to get involved, click one of these buttons!
So a “no myth” game was originally defined as a game where the game state wasn’t fixed until it entered the shared imagined space.
That means that “no myth” is a property of the ontology of the game. Something exists if it’s put into play and doesn’t exist if it hasn’t. (“Put into play” can also include things like “OK, before we start, I want to say that this game is about Darth Vader in a shopping mall speaking french so those three things definitely exist”.)
The GM in a no-myth game can think “I really want to put this blue chair into play, I’m gonna do it to the first normally furnished room the players enter, I feel such a strong attachment to this particular quantum blue chair. It’s gonna get in for sure. Oh blue chair my favorite” The fact that the GM is really into this blue chair does not make the blue chair half myth or the ontological state of the game “half myth”.
This means, logically, that the phrase “half myth” can’t meaningfully be defined as “some specific offscreen entities are canon, some are not”. Because that’s already what “no myth” means.
Instead, for a meaningful definition of “half myth”, how about: “some categories of offscreen entities are canon, some are not.”
“Hi guys, I’ll run everything in Duckburg fully prepped, but things over in Gooseburg is more ‘no myth’.”
“Hi guys, everything related to combat is improvised and ran ‘no myth’, I’ll just throw orcs atcha according to my own whim, but I have prepped all the entities and rules regarding the big fashion show in Veluna because I know that that’s the aspect of play that we’re the most invested in. Clothes, designers, audience reactions—all accounted for & implemented. Only with a steady whimsical stream of orc with murderous intent.”
What does this mean for Burning Wheel? It’s more of a no-myth game innit? There is no category of entities in the game that can be consistently expected to be solid.