I have a Nexus 6P and its battery is going bad. It just shuts down when it reaches 20-30%. Kind of annoying because I never know quite how much battery life I actually have remaining.
My Android (1st Gen Moto G, running Lineage OS, about 3 years old) shuts down once the battery level hits 15%. You can actually see it change from 15% to 1% for one brief moment before it shuts down.
Sure, the battery is old, but this behavior is unlike the behavior of any other OS/device I've seen. I've seen some laptops with seriously messed up batteries and as far as I can remember, the OS reports a smooth discharge profile without steep drops and without and strange "surprises".
I think Android is probably not taking battery health into account when it reports remaining capacity, but that is only a guess.
It is a bit tricky, but well worth it.
100-60 is still decent.
https://www.makeuseof.com/wp-content/uploads/2012/02/power_s...
My Samsung Android phone shuts down at 5-7% battery life. And the battery dies much faster these days. But it's never "inaccurate." It doesn't jump from 50% to 2% over a course of five minutes.
Other than something else being wrong with your OS, my only guess there would be the battery got bad so quickly the OS hasn't adapted to the new life cycle yet by removing enough of the old datapoints.