There is a backstab as in: "Ohohohoho, I am sneaky boi and can attack this guy without him having any knowledge of my presence at all!"
And then there is backstab as in: "Oh noes, I have no other ways but to dodge in order to defend myself from this guy who just jumped behind me, clearly he have a much harder chance of hitting me now, when standing behind me, where I can not really block or parry his attack, but only dodge, as opposed to when he is in front of me when I have greater variety of defense mechanisms."
At the end of the day, this is a general flaw in D&Ds turn-based systems, rather than BG3 itself.
Wrong there is no character facing in tabletop 5e. That is the point of perception... it is believe you are ware of your surroundings and your character is looking all around them for the fight. It makes no sense to be staring at a wall during combat. That is why tabletop have never used it outside of an optional rule.
