Why is my Apple Watch Series 11's battery life drastically reduced after updating to the latest OS?

I upgraded to a series 11 watch at the end of October before *OS 26.x was released and was enjoying excellent battery life. I would end the day (10pm to 8pm) with a more than 60% remaining. Now that I have everything at the latest OS release, I am seeing battery life drop. At 7am I am seeing the same amount of battery remaining as I used to at 7 or 8PM. One day this week is dropped to 21% by 6PM. I restarted after that, to make sure any runaway processes were cleaned up. But this is still much worse than the series 7 this was meant to replace, after 4 years of service.

Any ideas? This is clearly a misfeature of some kind but is it in macOS or iOS, since they are so closely connected?

[Re-Titled by Moderator]

Original Title: Series 11 watch battery life draining with all up to date software, much worse than series 7 watch. I upgraded for battery life improvements as well as features. Not seeing the win yet.