It works fine for me (not female, so no cycles to track).
I have a sleep schedule set from midnight - 7:00 am with no alarm set. I turn on sleep focus manually when I go to bed, which is almost never right at midnight - sometimes it's 10:00, sometimes it's 1:30. Sleep focus turns off automatically at 7:00 am, or I turn it off manually if I get up earlier. It took the 5 days it said it would to establish a baseline, and I've had nightly temperature data ever since.