Live Rock

[Van down by the river]

Before I get flamed, let me share a personal observation. Earlier this spring a friend of mine gave me some rock he had stored dry for 3 years.... we're talking pearly white here... not a SNIFF of life... I was going to use it as base rock, but rather decided to "cure" it as I wanted to make sure it had never had copper etc, as he used it in a fish only system... I kept it in a Rubbermaid container using a powerhead for circulation, and the change water from my tanks that I changed once a week. Kept this way for two months, receiving nothing but room and a little sunlight, I was AMAZED when I removed it to find patches of coralline algae and at the bottom of the Rubbermaid I had pods, mysids... you name it.... the rock was indeed ALIVE.

No flaming, just reviewing the facts.
The rock was dry, at the end of the story you deemed it alive.
A quick review of your process quickly explains the "magic" appearance of organisms. I think it's quite obvious. They came from your existing tank. When you changed water you added coralline algae spores, nutrients,mysids, and copepods. Many of these are very easy to miss. With the addition of water and nutrients the algae settled and started to grow. Many species of coralline algae can survive in very low light. Now with nutrients and microscopic algae and nutrients the Copepods have a food source. Without predators even a little food can sustain them.

But we are comparing two different Items. For seeding Dead rock I think this is actually a great method and very similar to what I suggested above.
This is a great example of organisms ability to colonize.

What we are trying to prevent is him paying for good live rock and losing the majority of the life on it. Sure he could eventually get the coralline back, and SOME of the original organisms, but why take two steps back to take one step forward.