It's because this VN itself isn't being overlooked by the original novel's creator Hinaga (Twitter: hi_na_ga) where the VN derives from
It's moreso like an adaptation into the VN-esque like how anime is made by a production studio adapting a manga into animation for anybody to enjoy
The creator of this VN, Kurosawa has asked for permission from Hinaga-san if I recall so everything's fine in that regard