You're absolutely right... it's a game. Larian could do whatever they wish. Then again, what's the point of utilizing an IP and Ruleset for your game if you're not planning to adhere to that IP and Ruleset as closely as you can within the limitations of PC game? And if you do adhere (as much as you can) to the rules, then there are going to be some things that are possible in one ruleset that are not possible in another (and vice versa) while maintaining a fun player experience in a medium (PC gaming) that cannot adapt rules like a human can while still being accurate enough for those players that know the ruleset and those that have never used that ruleset before.