Charwoman Gene
Adventurer
Defining a game mechanic during play is not role-playing and consistently requiring a player to define those elements just says the game cannot mimic reality without constant redefinition into something other than what it is. Lack of operational symmetry is a fault for any kind of role-play. Requiring constant redefinition of such makes the game a "playing of the system" instead of a playing of the role. It removes the exploration / education a player has within that role and leaves absent that portion of the system the game element was designed to simulate in the first place.
Why don't you just say narrativist play is badwrongfun? Its much more concise.
Roleplaying does not require precise world-physics/game-rule correspondence. I find that games with such an occurrence to be hijacked by players who want to set themselves up as kings in a faraway desertl and because the found a decanter of endless water. Give me an interpreted game and I can come up with some awesome stuff.