As an elite road cyclist and a Garmin Fenix user (has PulseOx), I can tell you that it is useless. For cases such as elevation adaptation, or asthma/COVID medical issues, it has some benefits but not many others. Your V02 Max, power, and HR are much more relevant data points.
I will also highlight, though my AW5 has the most accurate optical HR around, it is still nowhere near as accurate as chest-strap/electrical monitors. Same can be said about the wrist based PulseOx, will not be as accurate as finger tip. Not to mention it is a metric limited in its utility.
My hot take - it is a marketing gimmick and we won't see it come into workout metrics.