I don't think this interpretation is correct -- at least on Earth, there are no fundamental geophysical processes which can sustain oxygen in the atmosphere at

I don't think this interpretation is correct -- at least on Earth, there are no fundamental geophysical processes which can sustain oxygen in the atmosphere at anything but trace levels. Producing oxygen is not energetically favorable under basically any circumstances. Free O2 production was "invented" (as it were) as a way of murdering almost all other life on earth at the time. It's a mistake to look at life in a thermodynamic equilibrium sense unless your time scales are ridiculously long (i.e. burn-out-of-the-sun long).