https://wccftech.com/macos-11-3-big-sur-will-fully-charge-your-macbook-ahead-of-a-calendar-event-so-you-dont-have-to/

According to code found in macOS 11.3 Big Sur, Apple is planning to add more smarts to the Optimized Battery Charging feature.

With the release of macOS 10.5.5, Apple introduced a new Optimized Battery Charging feature that learns from your MacBook usage habits and draws current from a wall adapter to charge up to 100% only when needed to reduce chemical aging of the internal battery. Sounds like a genius idea, and it is, especially if you use your MacBook in a desktop-like setup, but it can actually end up deceiving you.