But this isn't true. It's possible to play narrativist using actor stance almost exclusively.Narrativism allows for/requires increased transparency that a. enables author and director stances more readily than trad (just to pre-empt: I think all stances are utilised across all playstyles and by different persons in different proportions)
I've done this, using AD&D and Rolemaster.
And as I've posted upthread, when I play Burning Wheel I am almost exclusively in actor and not author stance. And that game doesn't use unadulterated director stance - actions that establish setting elements (eg Wises and Circles tests) are declared and resolved from the perspective of the character ("I seem to remember that . . ." or "I look about for a person who . . .").
Narrativst play requires "a) rising conflict b) across a moral line c) between fit characters d) according to the authorship of the players". That's it.