I think you are missing a very key quote. See page 4 bullet #2.
In most pools, increasing the pump running time above two hours results in imperceptible improvement of water quality.
They are also saying that the pools were not the same and had "wide range of physical characteristics". Which means the turnovers were not the same (see below).
Actually it says most pools require 4 hours or less, not 2, see page 12.
Not quite. It says most pools can be maintained in "Sparkling Condition" which is different than the above quote which references water quality. This one is more about aesthetics while the first quote is about sanitation. They are different and require different run times but aesthetics is optional while sanitation is mandatory. But if you read on in that same paragraph it does mention that running 1 turnover is only necessary when removing dead algae. So they are basically saying the same thing we are that turnovers do not matter in day to day operation. They also give a range of a turnover from (6 to 12 hours) for study pools which also confirms that the pools in the study do not have the same turnovers.
They suggest 2 hours as the minimum, see page 13.
No they said the minimum does not exceed 2 hours which is different. There are some pools that can get away with less than 2 hours. This is consistent with the page 4 bullet above. Plus, we have already proven that with forum members (and myself).
So when you tell people "only run your pump for 2 hours" it doesn't do the study justice.
Actually, as I mentioned before, in pool school we do say to start at the 4 hours mark for full speed pumps and 8 hours for low speed to be conservative. What I usually tell people is most pools can get away with less than that and 2 hours per day is not an unreasonable target. Not just because of the study but because many of forum members have reported that they too can run for very short periods of time without ill effects. But the study only focuses on run time and as I mentioned above, it does say that a turnover is not necessary.
With a lot more measurements and time, could they have shown a correlation of water quality to turnover (or fraction there of) to water quality? Perhaps but as I mentioned before, that may not exist because the number of returns, skimmers, pool shape and how the water circulates in the pool, along with pump flow rate, determines how long a pump must run to properly circulate the water. This goes beyond the turnover calculation because two pools with the same turnover may not achieve the same water quality because they have different circulation patterns. So again, I still believe turnover is a very poor indicator for run time.