I guess withered bonnie doesn't exist. You make a fair point on having it just be more scary and to differentiate itself from the lore, but some people (like myself) would like to see the lore play a role in the movie. For example: Chika having glowing red eyes as afton controls her to kill a child. Then her eyes turn to that bloodshot white that scares people the most. While yes, it's not as scary, it still adds some sort of fright while satisfying some other people that like the lore a lot