I doubt that any encrusting coral completely blocks diffusion of water thru its membrane into the interior of the live rock. Of course the bacteria cultures in the interior will be different than the bacteria on the coral surface....
...I don’t require nitrification chemistry as
I am going to avoid the biodiversity part for now, but want to touch on two points.
First, we can ignore nitrification, but we can't avoid it. It a foundation of the life in our systems. We can try to feed heterotrophs or coral in a manner that allows them to consume theoretically first, but the nitrifiers are in the background expanding and contracting to pickup the slack. I think Randy's idea has merit, but I also think that he realizes in reality we can't really change much other than maybe provide less surface area for them to colonize, but that is a guess, because we don't really have grasp on what that threshold is, at least at the hobby level in any given tank.
Second, the idea that live rock is full of bacteria is a bit of a myth. The porosity and permeability of each rock and rock type is different. We often confuse porosity with permeability, they are not the same. In general there are no bacteria inside of rocks. Some rocks may diffuse minerals, but they are not wet inside either. Let's ignore water microscopic water molecules fully trapped in the structure, sealed from the world since the time the rock was created.
Aragonite is a crystal, the open spaces between molecules are smaller than bacteria by maybe 100 times. Ignoring anaerobes, bacteria need flow and oxygen. “Live rock” is alive on the surface and in the pores that are large enough to allow oxygenated water to flow.
A rock may be riddled with holes like a sponge and those tunnels may harbor bacteria, but looks are deceiving. Take Fiji rock for example: some is porous and some is extremely heavy and dense and solid.
Certain Fiji rock has a rough pebbly surface, but ocean conglomerate rock that is basically solid. On the opposite end of the spectrum, a piece o pukani from Fiji, is extremely porous like a sponge, and therefore has much more surface area where advective (that oxygenated water) flow can harbor life.
The point being, that for our purposes rock supports life where oxygenated water can flow, that is mostly the surface structure and any continuously connected pores that allow water flow. Deeper than that, the rock is basically dry and void of life. The pores that are dead ends and restrict flow may become anaerobic, but like their aerobic cousins, this is surface life too.
