As an experiment, I've done some extreme battery tuning of the operating system, the apps, and of course, battery optimization turned on, I eked 74 hours of battery with 8% remaining on my Pixel Pro 7 That was under extremely light usage. On the other hand, when watching a 23-minute YT video, my phone lost 2% battery! I've seen similar losses calling on Signal, which is a heavy-CPU user because it continuously encrypts/decrypts phone calls.
One thing a lot of people don't realize about battery optimization is that it does nothing for the currently running application, the foreground app, but it definitely stops running background apps only if their battery is set to Restricted, certain permissions are denied, and certain privileges are removed (all available through Settings). For example, right now on my phone, I have six foreground apps (5 are Android and 1 is Forecastie) and 13 background apps; Android stuff (10 apps), Google Play Services, DAVx5, and Signal. That's it. With this particular optimization, I have 30% battery remaining after 36 hours and I should get about 48 hours with 8-10% battery remaining.
My takeaway is that the phone's battery is optimized for no usage(!!), but once you start using it, it can drain quickly depending on how heavily you customized the battery savings.