The way that I understand Ambient Display is that it's supposed to adjust the screen brightness based on the surrounding light - ie: If you are inside and it's relatively dark - The Ambient Display should automatically dim the screen brightness & if you are outside in the sun - Ambient Display should raise the screen's brightness to max depending on just how bright the sun is 🐧
@Yoshi is right, Ambient Display is Google's version of AOD. If I remember correctly, there were a few optimization/QOL changes made in the recent update, which is why you may be seeing battery activity on your end.
