they'd be as undefined as the narrator,
What makes you think the narrator is undefined?
Because they're a narrator?
Means nothing. Stories are frequently narrated by a character, even when it isn't written in 1st person, and it's not an uncommon literary device to only reveal it at the end. Ever played Icewind Dale?
They speak in the present tense describing what we're seeing and feeling and they have, as yet, not been defined. And I don't believe that Larian are such elegant storytellers that they're going to subvert our expectations and have the narrator be an actual character who exists. If they do, then it'd probably be a fourth-wall breaking gag.
Larian took on a bunch of extra writers for BG3, it's not being written by the same people who wrote the DOS games. There is an awful lot of nuance in the narrator's voice performance for it to be a completely neutral narrator.
