The game has fewer CG than the previous games in the series, but the H-scenes using the map/battle sprites are more elaborate and involved. Need 100% CG/scene file because actually unlocking them all manually is a huge amount of work.
I think that makes sense. There are high resolution assets for a full-length videogame (the default option is the pixelated look but better assets are there), and due to the H-scenes that use the map sprites, there's about 100 voiced eroge scenes, plus all of the visual novel aspects of the game.