The best laid plans…
Apple designed that feature to be so smart, and unobtrusive to users that for some users, it entirely fails to work. Don’t conform to a regular schedule, or follow a predictable pattern? It’s not smart enough to compensate, won’t engage, and the result is a 100% charge anyway. Opaque, overwrought, and too clever for its own good.
The Battery Health metric is similar. It’s not a simple reporting of the design capacity vs. current estimated full charge capacity, which can be read by some apps; the algorithm includes other factors, but they’re not publicly known. In practical terms, it also fluctuates, as a result of software updates, with new versions sometimes reporting somewhat disparate figures.
And for a company that usually aims to insulate users from technical details that many won’t understand, or misinterpret, presenting that metric as a numerical percentage figure was a big UI failing. That decision has lead to a contingent of OCD users obsessing over ever change, minute or not, in the figure, like the gospel, without comprehending that it is, at best, an estimation, not the result of any sort of repeatable empirical testing one would undertake to gauge the health of a battery.
Something to keep in mind.
As a practical matter, most users aren’t going to worry about squeezing every last drop out of the battery by babying it as a best practice, or compromising the utility of their phones. When they do eventually wear out, the phone is replaced with a new model, or $69 for an Apple battery replacement, with that work covered for 90 days. If something goes wrong, they’ll probably replace the phone with a service unit, which will likely be in better condition than the one being serviced.
