Maybe they should have tested more TFP user's pools!
It should be noted that none of the pools sampled were outdoor residential pools. One pool was an outdoor public pool that also used ozone. It would be interesting to do this same study on pools maintained by TFP methods (ie- allow usage or higher levels of CYA and higher FC levels). Outdoor pools have the advantage of sunlight to further break down DBPs. Private pools also do not see nearly the bather load, which is emphasized as a problem for the creation and build up of DBPs. Also makes sense why the spas had such higher levels. They have high bather loads by volume and elevated temps creating more DBPs more quickly and likely limited exposure to sunlight.