Optimized Battery Charging option is on but Significant Locations turned off. How do I know if the feature really is on?

In that link, the screenshot of the lock screen is the answer. It will show what it plans to do, in that case “scheduled to finish by 10am”

I think this will happen when it has learned the pattern and the phone is plugged in under learned conditions. If you have the location setting off, it cannot learn the pattern.

edit: it probably uses an AI algorithm that looks for “significant locations” to make sure it knows what’s happening. If you plug your phone in at 10pm next to your bed or at 10pm in the car, it probably will want to charge different. If Apple documentation about settings says “must,” they mean it. I think the difference is the setting for optimized charging being on vs the feature activating