I am skeptical about this theory that biotic factors are solely responsible for creating 21% of atmosphere (around 40 million moles of oxygen) and I couldn't find any research articles which tried to model this process; the theory itself doesn't seem complete.
The present theory doesn't take into consideration the possibility that aerobic respiration would have co-evolved with oxygenic-photosynthesis and how the atmospheric oxygen levels stabilized at 21%. It is not illogical to assume that because cellular concentrations of oxygen will be high in cyanobacteria; it is possible that using oxygen as electron acceptor is a mechanism of preventing oxidative damage.
Another point, though it is not a logical justification to doubt the theory; it just seems too astoundingly unbelievable that life on earth was dependent on an organism? How did cyanobacteria flourish so much? How did photosynthesis overtake oxygen production by abiotic reactions such as UV photolysis of water (which seems plausible)?
Assuming that population of cyanobacteria is limited by total available water (which will always be less than the total sea surface area x ~2m [limnetic zone] ), 12 hours of available light, and possibility of coevolution of aerobic respiration, how much time would it take to produce this much of oxygen. Is there any study which quantitatively proves this hypothesis ?