I don't think this is entirely true. Clearly sharing/netorase has been the main focus of this game so far. But the overview very clearly suggests that a cheating Luke, will result in that part of the game's focus shifting to netorare. Obviously, we're not at that point yet, because Kathryn is still unaware of Luke's betrayal. But she is showing signs of becoming suspicious of some of his actions, and has half-heartedly mused on the possibility that he might be cheating. None of that would happen if we weren't heading towards an eventual netorare route.
If you're not allowing Luke to cheat, then obviously it will never happen for you, and the game will retain it's sharing/netorase focus. Fortunately, the way the game is set up means the Dev doesn't need to add a lot of additional content, to have a separate netorare route. Mainly, all he needs to do with Kathryn's content, is have her not tell Luke in advance or have her fail to share knowledge of her adventures completely, and netorase instantly becomes netorare.