I don't really understand Stevelin's point because it seems to just be headcanon they're discussing like it's fact, but those theories have little bearing on what's actually in the game.
As for you SteelTempest, that's an opinion a lot of people share. The issue isn't that Tav isn't a chosen one or that Tav is a blank slate. It's that they are entirely ancillary and not even really a character. One Tav will end up playing pretty similar to another if you play a good character. I at least found that by the second or third playthrough my Tavs felt quite boring and samey. If you want an example of those same things executed on in a far more satisfying way, I direct you to Pillars of Eternity and the Pathfinder games, kingmaker in particular. Both games have you play blank slates that aren't chosen ones at all, and they consistently keep your story as the centre of the narrative, whereas in BG3 I find that Tav is just a husk you use to interact with the world, and isn't really meant tobe a character.