Spoilers for BG2:
Viconia's son grew up with a loving mother until she was murdered by the agents of Lloth. Then his father, the Bhaalspawn, pulled him into his private campaign of vengeance in the Underdark against the Drow and Lloth. That is fairly specific. As vague as the answers your character in BG3 can give, they aren't actually vague enough. The answers you give are assumed to become fact or truth.
If there was a (Lie) option that could also work.
Can you give me an example of what answers are too specific? At best you can confirm or deny that you lived in Baldur's Gate as far as I've seen.
