Oh I think you misunderstand - I don't think that will be her path, and I think that she'll look for other relationships if she can't get Nika. The point being, what will she do if you chose Sasha, or Sonya, or Nia, or any of them? She won't be happy. We already see her expressions change depending on what you've said when. If you try to be on her path and interact with anyone else, she gets (naturally) jealous. I don't think it will lead to a good ending, but it's probably part of how the throuple's develop. I'm not talking about dark paths so much as NIka is kinda clueless about all this. He had a relationship when he was yound, it wasn't a mature relationship with mature decisions, whatever his feeling were. He can fuck up through arrogance, or through ignorance. I don't think he would intentionally exploit her so much as get caught up in his own head.
I also think every LI will have some different challenge for Nika to work out, and I'd be surprised if Ocean didn't have 'bad' endings, (seeing one of the steam achievements was avoiding kissing anyone or something like that, I'd be surprised if Ocean doesn't account for a path where someone is modest as well as a path where someone is a manwhore).