Hello there,
the harem route was just called like that because it was Anna and Charlotte ending. Plus being able to get each of the girls in their respective routes. Full on Harem wont be a thing since most of the girls are not fine sharing with multiple, not all are fine with every other and is not really the focus to make it a regular harem were they all just get along and are fine with Mc just banging the whole city.
But yes, preferences exist for a reason.