Great info here. It compares high tech tank, EI dosing, co2, high light, just one half no nutrients in sub and the other half with nutrients in sub (root tabs/osmocote).
http://www.plantedtank.net/forums/33-plants/876457-so-called-heavy-root-feeders-fact-fiction.html
Looks like you can get great growth with just water column dosing, but the heavy root feeders due look to benefit a bit more from nutrients at their roots.
The heavy root feeder looked to in a better shape with nutrients at their roots (without, they still looked decent).
If you had a high CEC (absorbs nutrients from water) substrate or nutrient enriched substrate (soil, etc), you wouldn't need to add root tabs. Inert low CEC substrate would need root tabs if you want that extra fertilization.