My problem with the study was noted by your second citation: There's insufficient information on the content of the pool water. FC look like it was 1.17ppm but there's no mention of CC, or pH, T/A, CH, metals, or other content of the water other than a very oblique comment about keeping the water free of contaminants, whatever they mean by that.

Nor was there a discussion of the variations in the water for each swimmer.

It's kind of like comparing 1/4 mile times of cars, but not allowing for barometric pressure, or whether sometime the course was flat and sometimes they had to go uphill or whether the surface was dry and sticky or a bit oily and slippery.

Still, it's a start. But as Ben posted before, what's the risk of water-borne diseases WITHOUT Chlorine?