I think clay has a very important role in blocking antinutrients and making h2o truly available for your body. I live in Perú where Andes' people used clay as a dipping to eat with very poisonous vegetables. For example, potatoes, when freshly harvested, has very high toxic content (traditional native potatoes) so this people make this sauce out of clay and vinegar for their potatoes.
Second, clay, when uncooked, make water alive and highly bioavailable. When you drink plain water, with insignificant mineral content, it passes through your bowels and just push your stools. But, when water is loaded with clay, it acts as a medium of transport, exchanging different types of ions and deloading your body from waste particles (toxins)
I don't know the science, but it is what practically people has use it for before. The Incas where a very legume and grain dependant civilization. For that, Clay was a staple. in this kind of diets, dirt is very important. Not only for minerals but for microbes.
I use a minimal amount of it just until my water stops looking clear and gets a slight white tonality. The reason I use it is for high amount of pollution is in the city water and air.