Facing is an optional rule on page 252 of the 5e Dungeon Master's Guide, and it does grant advantage to people attacking from behind. So, it's not just something Larian made up.
Like flanking, it's an optional rule for a reason. Solasta has proven that we can have everything 5E has translated into a computer game. I want this but with full 5E Faerun with Larian's graphics budget. Giving us full 5E shouldn't be hard if a band of nobodies were able to pull it off with the SRD rules.
