pool closures

i have always been a big supported of the CDC - they seem to keep public health in the forefront, even when it is politically unpopular.
Of course i am writing today because i am questioning something.
In the fresh, treated recreational water section - there is a little part talking about closing a pool for only 20 minutes after raising the free chlorine level to 2 when a "formed" stool is found.
The assumption is that a formed stoll has not 1) started to dissolve by the time it is found and 2) only has E. coli as the creature to be concerned with.
Again the assumption is that a "formed" stool means that the person was not sick and e. coli is all that has to be worried about.
I have to say that i am not convinced that these assumptions can be made and that any fecal event should be treated the same - 13 hour closure with free chlorine being raised to over 3 ppm. (they say 12.75 hours, but i am not splitting hairs with 15 minutes).