I don't really see that being the case here though. In the trailer she certainly didn't move like a 3D character and I don't see it in this visual either so I'm not sure where you're getting that from
The new character designs are much closer to the original designs from the light novel. She's supposed to look fairly young. Iirc she's described as looking like a teenager.
I feel like that's more because of the more modern artstyle instead of actually making her look younger
