to me, “fiction first” means you cannot invoke the mechanics without having a proper trigger or position in the narrative, and the mechanics primarily create more narrative, but importantly, the mechanics are there to drive the narrative in specific ways, and ignoring them does the game a disservice

While I agree to the latter, to the former part of your statement it ignores both non-diegetic mechanics —plot points in Cortex, the hinder mechanic in Cortex not requiring a fictional trigger, plot points in Fate — and Vincent Baker himself saying moves in AW don't have to.

Honestly this has always been my go to. Like you can't ask to have a perception Check off the cuff because I asked what a passive was. But if your pc in the narrative noticed sowmthing off then yes that would lead back to a mechanical resolution

that’s probably the best definition. “fiction-first” games treat interesting narratives as the primary goal of their systems, not as a byproduct. fiction-first games almost never treat rules as optional. the games are already so mechanically simple that any existing rules are likely load-bearing.