In low fat diets, our gall bladders aren't filled with fresh gall regularly and sediment builds because they only fully empty when we eat high fat foods. Over time, the sediment causes back pressure on the liver, so the gall forms into liver stones .
Flushing is a way to go "over the top" in fat consumption, to trigger the flush response and clear the sludge a lower fat diet might permit to build up.
If you drink a bunch of good oil, once or twice per month, and eat low fat the rest of the time, you help re-balance your Essential Fatty Acid mix. The average person eats so few good fats that this high level dose is ok, whether it is absorbed or not.
I've lost weight with flushing, not gained. I've always assumed that it was water weight, however. "Butt Pee" drains lots of fluids...
The Pericone guy thinks eating more of the right fats makes (beautiful but aging) women more beautifully youthful.