The difference with playing tabletop and this game is that Larian has incorporated the height and dark advantage/disadvantage system. Most of the time when I DM on tabletop I don't give bonuses or penalties for those situations, because they're not really in the rules. However here we have to consider it and it does make a degree of sense. So percentage is just an easier way to broadcast this to the player. I agree the element of the unknown is taken out slightly.
