I’ve had my watch a little over a month now, my first apple watch and been very happy. One thing I’m confused on is how the optimized battery charging works exactly?

My charging habbits are pretty much like this: in the morning when I shower & brush teeth I charge a little, afternoon when I finish my workout and shower I charge a little and evening before bed as I’m getting ready I charge a little. This way I keep the watch between 20-80% most of the time and it doesn’t take any effort for me.

However, if I forget myself or take longer to shower, the watch always blasts past 80 and charges to full immediately, I never get the optimized charging icon where it stops at 80%. Even though my charging habbits are pretty consistent. What gives?