Substrate Gold, Eco-Complete and similar substrates do contain some nutrients so I guess you could say they are "Fertilized substrates". However flourite and laterite, besides their iron content, don't really qualify as fertilizers. It's true that they will absorb nutrients from the water and as they age, they will be able to provide many more nutrients, this is true for just about any substrate. But in this case I am referring to additional fertilizers, these usually contain both traces and macros, usually in the form of tabs of some kind. Some use jobes sticks, AP root tabs, Flourish tabs, rich sands, home made pellets....
Many people rely solely on water column fertilizers, others use both substrate and water column fertilizers. Some, usually lower light tanks, only fertilize the substrate and don't add any additives to the water at all.
I for one fertilize all my substrates. Soil, sand, flourite.... they all get extra ferts, just in different amounts or forms. Flourish tabs have to be my product of choice for most substrates.
Giancarlo Podio