Yeah harem is posible even if you chose scene with one girl over another. They kinda dont have traditional path. If girl end in harem or not based on love and lust points. If you colect enough points with girl she would end in MC harem.So Harem is still possible but you have to play their solo path before?
I was pretty by this update because you had to choose between Isabela and Madison.
If you missed some scenes and some points, it doesnt mater you can pick them later.
So yeah no mater whom you choose Amber or Isabela later MC still can include them in harem.
Atleast from what I understand.