Yeah. When I did my first one of these 25 years ago, I had to prep with an enema. Ultimately, I don't think it flushed me out as much as the magnesium citrate I took yesterday (which I had to pay a few bucks for, so not literally free).
I've done the master cleanse thing a few times, where you only consume this water, lemon, cayenne pepper, maple syrup concoction for 10 days. It never gave me the immediate and direct flushing part that this did, but I think the end game is similar.
I don't know if there are any negative health ramifications to the mag citrate, but I could see doing that once every now and then to flush the system (instead of a liquid only 10 day fast). As you say, it seems intuitively like a good thing for the body.
Anybody know more about the relative health benefits of this?