When did WatchOS start offering optimized charging?

Greetings, just wanted to share something interesting I discovered on my Apple Watch SE (2nd generation) with everyone. I was checking my watch's charge level this morning using the Batteries widget on my iPhone and noticed that my watch hadn't fully charged like I expected. Naturally, I was a bit concerned... especially since I've only owned the watch in question for a grand total of slightly over two weeks at this point. I decided to power down the watch and place it back on the charger, and after a few moments the watch powered back on and showed me an interesting message.

The notification my watch gave me went something like this (paraphrasing here as I don't remember it word for word): Optimizing Charging. To extend the battery life of your watch, your battery will be charged to a limit of 80%. Tap the open charging ring to adjust the charging limit. Admittedly, I had never gotten a message like that before, but I did figure out that tapping the text that showed the charging status would permit me to resume charging the battery to 100%.

I'm not sure if that's a permanent change, but I suspect not. Wondering when this feature was added to WatchOS...