From my checks, the SpO2 readings on smartwatches are inaccurate. According to my Galaxy 5, to get an accurate reading, I need to have my elbow on the table, the watch farther down my forearm (instead of on my wrist), and raised to heart level. I never sleep like that. And if I try to sleep with my watch up that high, it falls down toward the wrist and gets even worse results because of bad contact.
On the other hand, an xPAP machine only looks at breathing. It detects when it is happening and when it is not. It can detect why it is not happening. It can, if an APAP, change the pressure to get you breathing again. It can determine a ton of other parameters. Then it reports this in data form so we can help fine tune our treatment. If a regular CPAP can only deliver, for example, a pressure of 12, then it cannot adjust to your needs at night. And if an APAP is set to deliver between, again for example, 8 and 15 pressure, but your body needs more than 15, it cannot go higher. BUT we can look at the data and determine if that 15 is not high enough.
Neither can report on body position. We can only guess that based on the xPAP's data.
Meanwhile, the smartwatch is sitting there, reporting meh data on what little it can detect while sitting on your wrist. For me, best thing is it's heart rate reporting.
TL,DR: calm down and continue to gather data. Get an oximeter. The more data you have, the better.
Take a deep breath and count to zen.