If you want to research Miracle mud, add the creators name "Leng SY". I think it was around 1994. It gained rapidly in popularity, then died off just as quickly. Some people still swear by it.
It's easy to measure failure in this hobby but it's hard to qualify and quantify success, much less attribute it to any one product or methodology.
There's a product available from plant nurseries called "PEI Mussel Mud". It's a marine clay that's used for planting water lilies in. I had a friend of mine send some estuary mud from a mussel bed in Nova Scotia, but it had wood debris in it and was a little too buoyant. One of Leng Sy's claims was that the slight buoyancy of his mud increased the boundary layer (the interface where water meets the media). You would lose this feature if you used it as a lower substrate below sand. You would still have the miraculous elements available to the algae, but the roots of macroalgae are simple holdfasts that keep it anchored to the bottom. Macro algae does not obtain nutrients through a root mass, it is absorbed through the blades (leaves).
The concerns most people have/had with miracles mud is the possibility of sub-miraculous heavy metals and nutrients bound in the mud. It is a substance collected from nature, so it cannot be completely homogenous. In the case of mussels, they thrive in nitrogen-rich high nutrient water so I wouldn't try the water lily product I mentioned above, nor do I infer that it is the same stuff.
Reef keeping is more science, less miracle. Miracle Mud has had 15 years to produce a bioassay stating what it contains and why we need it. Deep sand beds have their proponents and opponents but both sides bring some scientific proof to the table, and at worst sand beds are redundant/superfluous.
Stephen Spotte put it best with the forward in one of his aquarium books. "The successful maintenance of a seawater aquarium is mostly witchcraft mixed with a little science. In this book I have attempted to describe the science, but with the realization that understanding the witchcraft might be more useful."