I have OSA. Pre-treatment 10yrs ago, I had AHI of 89. I am otherwise in good health. Inherited. Love the CPAP, feel so much better. After getting CPAP, AHI dropped to ~1.0. If I had an Apple Watch with this, I probably would have sought treatment years earlier. I just thought it was a bad inherited trait, not realizing the stress it put on my body.
Will the Watch be the final call for those that it detects with OSA? Probably not, but it should at least make someone aware, that maybe they need further testing and treatment.