So you think the battery meter must be wrong, because you're getting good battery life? I have to say, mine has been pretty accurate from what I can tell and there have been updates to help improve battery in the recent updates. Maybe you're just lucky at the moment but I doubt your battery meter is broken in any way.
My 6S Plus (and the previous 6 Plus) are both @ 65% at the end of a 16-17 hour day on average. There have been places and times with something out of the ordinary like poor signal or extra heavy use but generally I see good battery life with my devices.