as far as it goes it's a good rule of thumb for beginners. the reality is it all depends on bio-load, and other filtration nutrient export.
for example, a 60g system can be ran with about 10-15lbs of live rock and a moderate/heavy fish load (between 6-8 baby clown, hoevens wrasse, baby kole tang, soldier crabs, cleaner shrimp and tons of other inverts, and roughly 50-75 coral frags and colonies ). how do I know. there is such a system up and running. always minimally detectable nitrate phos, zero ammonia.
extremely oversized skimmer, filter sock about 10-15lbs LR in sump none in display only a rack system for corals. particle sponge in sump between baffles, and weekly water changes of 20-40% depending on whose performing them.