Your character also get the [Baldurian] dialog options and makes comments about being from Baldur's Gate, including details about estaishments and people.
There's also the fact that if you add too much background to a custom then they are no longer a custom character, they're just another Origin character.
In BG1/2, CHARNAME had the exact same background as Imoen (Gorion's ward, raised Candlekeep, spoilers, etc.) and had zero personality. This was so that the player could do whatever they wanted and use their imagination. Good or Evil, any race, class, either gender, etc.
