Okay, it must be due to my creating a day or two ago a time period the phone couldn’t ring. We got tired of it going off and waking us. I set Bedtime Mode for 11pm to 11am, as our sleep schedules vary generally within that range, and late weekend movies often got disturbed too. I’m not sure why the display needed to change… it was just the ringer/notifications alerts I wanted muted. Our cell phones aren’t kept near our beds, but can be heard. Samsung might find it advisable to provide the gray scaled screen as an option within Bedtime Mode, rather than it being a mandatory part.
Thanks to Kizzy and all who directed me to my oversight and culprit. When setting it I didn’t catch the part about it including a display change as well as audio.