Night Shift Mode does not display Sunset to Sunrise Mode

I have iPhone X updated to iOS 15. Post the updating to iOS15, the Night Shift Mode under the Display & Brightness section of Settings, does not display the option of Sunset to Sunrise mode. This option was available in iOS 14.8. It only has the option to schedule a time for the Night Shift mode manually by setting a time. I called the Apple Support but they said that the feature is an enhancement of the iOS 15

The irony is the older iPhone 6s still has the option to schedule the Night Shift Mode from Sunset to Sunrise & a manual clock time.

Is iPhone user facing a similar concern?

Is there a way to bring back the Night Shift Mode to Sunset to Sunrise option?

Thanks