Yea, that's what I'm saying. He had the choice to do whatever he likes with the game he created. Didn't he say he particularly liked the shipping of Lychoris and that spoiled kid, and the heroine with the male lead? And he really seemed to like the idea of a yandere when Lychoris brought it up.
He writes his favorites down in his notepad, it's not a big surprise that he chose his own personal favorites to include in the game since he can't add all thousands of them. Maybe yandere is his fetish for all we know. The characters, particularly the love interests, might not really be yanderes here...there was just that one in a million chance that they'd turn out to be that he chose to include in the game.