Apple Watch doesn’t track sleep beyond ‘sleep schedule’ alarm

I have sleep schedule turned on from 11:25-8:50am. The past couple days I have slept through turning off the alarm on my watch (w/o touching my phone) well into 10am, today I didn’t wake up til noon. However the sleep app in Health says I woke up at 8:50 each day.

I like having sleep focus turn on automatically, but accurate sleep tracking is important to me. Is this working by design? I’d think my lack of movement and low HR should register as sleeping still.