Have you noticed the drop in battery life? How many hours can you run on battery? I haven’t found a battery support page for macOS but Apple’s support document for the iPhone states that
the battery information is “software design that provides a more accurate estimation of both power needs and the battery’s power capability.”
My iPhone 11, which I replaced with an 16 Pro, is still showing 92% capacity (it contains a copy of 1PW that I keep as a backup). My less than one year old iPad is down to 96%. The info you are seeing may or may not be accurate.