Makes perfect sense to me. Stomach size and digestion are going to, obviously, vary with species as those that are adapted to grazing on algae, eating readily available insects, or piscivorous fish will all have variations in digestive anatomy. Feeding a tank with a variety of species should be so much more complicated than we make it.
It seems to me like we have, say, a bunch of seed eating small finches, a fruit/nut eating parrot, a group of larger seed eating finches, a group of insectivorous swallows, and a random crow and we toss them all a mix of pelleted "bird food" and expect them all to eat the same thing, at the same rate and the same amount:weight ratio. It just doesn't make sense to apply a general rule of "this is exactly how much/how often" to feed these animals.
I think the best way to determine overfeeding is by how much food is remaining un-eaten, the body condition of the fish, and how quickly nitrate levels rise. Not a single one of those factors can be used alone, but all can be used together to determine if you need to cut back on feeding.