Sleep Data Sometimes all One Color…No REM, Deep etc Breakdown

Can you explain the fact that my sleep data for last night (the Sat vertical bar at far right) shows a single-color with no REM, Deep, Core, etc breakdown? I see a display like this periodically. My sleep schedule is set for 11:30pm - 9:30 am. It’s 11:21 am now and it’s still like this. My Sleep display today on my watch only shows graphs of the last two weeks, with the word “Consistent,” no last-night display like I’m used to seeing. But this does happen periodically and maybe there’s some rhyme or reason to it, but I haven’t figured the pattern/reason yet. Does Sat always show like this in the Health app until Sunday is done perhaps??? I would still like to see my night’s display on my watch. I still am trying to get the hang of the displays and settings.