You're claim regarding the FDA, is somewhat incorrect. The following link clearly explains the balancing act that Fitbit is facing, https://www.slashgear.com/fitbit-charge-3-relative-sp02-sensor-sleep-apnea-research-20541797/
and here is some of the language, extracted from the above linked-article, and copied/pasted:
"Still, it’s not the first time we’ve seen such promises from Fitbit. In fact, back when the Fitbit Ionic smartwatch was launched in late 2017, one of its boasts was a relative SpO2 sensor. At the time, the manufacturer said that – though the sensor wouldn’t be active at release – it eventually planned to use it to identify things like sleep apnea.
What Fitbit is reluctant to do is say that it can diagnose conditions like sleep apnea. When its new Sleep Score beta goes live later in the year, its models with a relative SpO2 sensor – including the new Charge 3, the Fitbit Ionic, and the Fitbit Versa – will track breaking disruptions “which can be indicators of health issues such as allergies, asthma or sleep apnea,” the company says.
However, that will be positioned as a way to better “understand” sleep, not to necessarily diagnose sleep conditions. 'Separately, Fitbit will continue to develop and clinically validate FDA regulated software as a medical device for various health conditions including sleep apnea and atrial fibrillation,' the company said today. 'Fitbit is one of nine companies in the FDA’s digital health software precertification pilot program, which is designed to streamline the approval process for software as a medical device.'
That transition point between a consumer product and a medical device is a tricky one. Fitbit isn’t the only wearable company to find itself balanced on the precipice between the two categories – Apple, too, is said to be flirting with more diagnostic-style functionality with its Apple Watch, for example – but the risks of inadvertently promising features that regulators deem too much like medical devices are considerable. That’s on top of questions around whether relative SpO2 sensors alone are sufficient to come to such conclusions."
