The point is to charge your phone over a period of time rather than topping it off as fast as possible, as this can degrade your device’s battery more quickly. But the way the feature is set up could be a little restrictive for certain users.
Google’s new feature seems to be rigidly time based instead of learning from how and when you charge your phone (supposedly like Apple’s does). I imagine it will "adapt" over time to get some AI.
Personally I’d like to see a charge limiter feature like many Asus laptops have, or my rooted Android phone has. It’s another reason I may not have to root my phone if I can stop charging at 80%.
See Google’s Adaptive Charging feature only works during certain hours
Google recently added an Adaptive Charging feature to newer Pixel devices, and it turns out the feature is weirdly restrictive.