Can Apple Watch 10 and Ultra effectively detect sleep apnea episodes?

The Series 10 gathers sleep statistics and after 4-6 weeks it will notify you if it thinks you have sleep apnea, and suggest you consult with a physician.

A co-worker got the Series 10 on day 1, and about a month later the Apple Watch told him it thought he had sleep apnea.

It is not instantaneous.

This is Apple's statement;

"The Sleep Apnea Notification Feature is available on Apple Watch Series 9 and later and Ultra 2. It is intended to detect signs of moderate to severe sleep apnea for people 18 years old or older without a diagnosis of sleep apnea. You can be notified if signs of sleep apnea are detected and receive a report that helps you navigate conversations with your healthcare provider."

You appear to already have a diagnosis.

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