One has to understand the quantities. If the pellet is 80%-90% protein and the wheat is mostly starch, the pellet can't have much of the wheat but very little, as opposed to the cheap pellets consisting of 80%-90% of wheat and/or corn -derived products. NLS uses wheat flour as a binder and the pellets contain a lot of wheat. RD argues that this is not bad at all for omnivores and herbivores but there is definitely room for improvement for carnivores=piscivores but the price becomes indigestible, AFAIU his point.
Clay uses egg white for binder = pure protein. RD is all for it and AFAIU thinks it is nice. What ticks him though are Clay's wide-sweeping claims that wheat etc. are bad as well as many other unsupported statements.
Anyway, can't lump all (cat)fish in one category. Can't do the same to the pellets. Wyckii is a predator. It hunts fish and crustaceans. Simplistically, I imagine his diet is ~90% protein as far as the solids and excluding water.
Predators have short digestive tracts that will not digest even aquatic hydrocarbons well, not to mention the terrestrial. Cheap pellets offered to an outright predator hurt their health in the first place and in the second mostly go through the fish undigested and pollute your tank water.
Omnivores have medium tracts. Herbivores have long tracts to handle hard-digest plants, as in part can be judged by how far the anus is from the stomach.
In fact, and this blew me away, omnivorous cichlids have been shown to lengthen their tracts in response to more plant-derived diet during certain times of year or in a lab and shorten it when fed more animal-derived diet.