Aren't these home-brewed tests of chlorine strength hopelessly inaccurate? Aren't the errors inherent in diluting a sample to this level simply huge?

We tell people to dilute water samples by 3 or 4 to 1 so they can test higher chlorine levels with an OTO test but then warn them that the results are just ballpark. Now people are diluting chlorine samples by 20,000 to 1 (or so) and talking about tenths of a percent precision? I dunno...