Let me try to address some of the silliness of some of the claims here that "nar" is defined solely by player driven, no myth play, where the player sets the premise by discussing what is for me a non-hypothetical.
Suppose I as a college age DM have a younger family member come to me and say, "I wanna play D&D" and I have no prepared solo adventure ready. So I let the player create a character and they create a 1st ed. AD&D thief. And then based on the character he creates and after a few questions about his backstory, I improvise a story on the spot about the characters adventures in a large urban area and his dealings with a gang of thieves he belongs to, and his conflict with a group of slavers who kidnap another street urchin. Now this is entirely player driven, no myth play, where the conflict is set by the features the player defined for their player character. This is "story now" play.
And then again, a similar thing happens with another young player and they say, "I wanna play D&D" and I have no prepared solo adventure ready, and this time they create a 1st ed. M-U, and after asking a few questions about the character, I improvise a story about a young apprentice whose master has just been murdered before he can finish his apprenticeship and who has to make his way in the world and is struggling (or sometimes not struggling) to resist the temptation of dark magic to help him survive the situation he finds himself in. Again, this is "story now" play in 1e AD&D. The play is driven by the character and what the player told me he wanted to test based on how he described his character and why he told me his character what wanted to become a wizard.
If that is all it takes to be "nar" then 1e AD&D is a nar game, and so is every other single system. And that means that "system doesn't matter". So clearly, maybe while "Story now" might always be a feature of a nar game, it's not the sole defining feature and there is something else going on here. Either that, or this is all word salad with no fixed meaning and everyone is taking away different things because of that.
Don't get me started on how much of this is just pretension of "I'm a better more artistic sort of gamer because my game is narrative and so its about a story and has real protagonism." Transcript as story is a feature of all creative agenda is something even RE acknowledged; toxic and pretentious as he might have come off at times, he didn't get that wrong.