My impression is that nothing is fixed with the iOS 17.2.1. On the contrary, the poor battery performance turned out to be even poorer after the installation of the latest iOS.
Two screenshots below with my battery performance within 10 days:
1) iPhone 15 Pro, battery health 100 %
2) iPhone 13, battery health 100 %
The red square in both screenshots marks the performance after the installation of iOS 17.2.1.
Picture 1 (iPhone 15 Pro): If you look at Saturday last week and especially Tuesday before the update: Both days I had an activity of 7-8 hours. Saturday the battery used less than 50 percent in 7 hours. Tuesday it used around 60 percent within eight hours.
Monday this week and Saturday after the update I had an activity of around three hours and it consumed the same amount of battery as on Saturday before the update (with a usage of more than seven hours). This is horrible numbers for a new phone which is supposed to be a premium version of the 15 series.
Picture 2 (iPhone 13): Compare the battery usage of the iPhone 13 to the usage of iPhone 15 Pro and you will see it performs a lot better. But also here after updating 17.2.1 the performance has been impacted negatively, but not as radical as on the 15 Pro.
I am very tired of this. iOS 17 and iPhone 15 have been out for three months now - and nothing changes for the better. Frankly, the 15 Pro is the worst phone I have had when it comes to battery performance.