Battery health

have you read

About the battery and performance of iPhone 11 and later - Apple Support

and maybe 

iPhone Battery and Performance - Apple Support

and Batteries - Maximizing Performance - Apple

people report apple does not change the batteries until they are lower than 80% in health

Sometimes it plays catch up all at once or in cascades. It's unlikely that it actually stayed at 99% that long, then lost another 1% in two weeks. It's also an estimate.

In any case, there are things about it where it's not really worth worrying about all the time. It's not a real time indication of battery health. It updates at times that seem almost random.