No it doesn't. Live rock is no different (fundamentally) than bioballs. As long as it's kept wet the bacteria live on. Lets look at the ocean as an example. Does the reef or rocks ever come out of the water.. Ahhh yea..
You could easily strap LR
rubble to a board and run water over it and achieve the same thing. All that's special about LR
is a) it made of calcium carbonate and b) it looks nice in a tank.
If as a society we decided tomorrow that blue balls (uh oh.. will Dragon edit my blue balls comment?) looked better in a tank than LR
then the LR
industry would be on it's way out and everyone would start touting the need to blue balls to be submerged and how beautiful it looks in all it's blue glory.
BTW: the lighter the rock (in general) the more nooks and crannies for bacteria to live. Lighter the better. That goes for all those who think they get a lot of anaerobic activity in their rock and sand bed too