Suppose a group is playing Moldvay Basic. The PCs enter a room in a dungeon with some bandits in it. The GM makes a reaction roll, and it is reasonably extreme - either hostility, or friendship.
Why do the bandits react to the PCs that way? The GM has to make something up - the PCs remind the bandits of an old enemy or friend, are wearing something taken from/lost by the bandits, etc.
I don't see how narrating consequences in a flashback is, at its core, different from this. The "past" of the fiction is always up for grabs in a RPG, and new things are being established about it all the time in play.
Why do the bandits react to the PCs that way? The GM has to make something up - the PCs remind the bandits of an old enemy or friend, are wearing something taken from/lost by the bandits, etc.
I don't see how narrating consequences in a flashback is, at its core, different from this. The "past" of the fiction is always up for grabs in a RPG, and new things are being established about it all the time in play.