alright so it’s “stupid pomeranian uses it wrongly”:

quote from apple:

“When the feature is enabled, your iPhone will delay charging past 80% in certain situations.

…

Optimized Battery Charging is on by default when you set up your iPhone or after updating to iOS 13 or later. To turn off the feature, go to Settings > Battery > Battery Health & Charging and turn off Optimized Battery Charging”

… so reason is : after major version update,

Apple

is simply turning this setting ON

i hate Apple