Oxypowder is supposed to "break things down" and melt it into a liquid mush. As it melts/breaks old fecal crap down and it comes right out.
The other products bulk and scrub the old crap out and "push it out" like that. Add fiber/psyllium to crap and you get formed stools. All it does is thicken/bulk it up and that's why there seems to be more coming out.
So depends on the product what you're seeing and getting, but it's all cleansing in one way or the other. On the Master-Cleanse people think all the dark brown they're seeing is actual melted crap when it's mostly senna tea they drank the night before and maple syrup.