Increasing flow and decreasing concentration through most filtration assemblies generally increase their effectiveness. There are some exceptions in certain active transport systems that I can think of and the kidneys certainly do some of that, but even then the system has to be operating above a certain optimal flow.
Healthy skepticism that this makes a difference in day to day human health may be warranted, but skepticism that the claim is even meaningful in the first place is not. Your body does routinely contain a lot of toxins, and it has mechanisms to clean them out. “Polluted” is not a binary yes/no attribute anywhere else in the world and it hits not binary in your body either; it gets more or less polluted as it excretes less or more waste.
Sure, if you’re dehydrated, your liver and kidneys will probably have a hard time doing their job. But drinking more water than you need, drinking magic teas or vitamins, etc does nothing more than what your liver and kidney normally do in a healthy body.
Metabolic byproducts are literally toxic, and your liver and kidneys remove them constantly. "Detox" is probably overused but your comment is wrong too.
What does that even mean? If your body contained toxins that you needed to « detox », you’d be having a pretty bad day and kidney failure.
Detox is meaningless. It’s not like your body is « polluted » and and you can only clean it by « detoxing ».