I don't care what the reason is and I don't own an Xbox Series S so I don't care if that's the problem. I don't want a single player RPG to have co-op and for what? To satisfy the dozen extra people that will play the game? Nah. I care about what I want and what I want is a great single player RPG from Obsidian and that's what im getting.
As for Xbox Series S, it's great for parents with kids who don't need the high end shit since all they play is Minecraft and Fortnite anyway but it's a shit console due to the lack of RAM but I don't own it and never will so whatever issues or problems developers/publishers may or may not have with it has nothing to do with me.