[reefgeezer]

It's simply a matter of risk management. You really don't know how much dried organic matter is contained in the rock. Additionally, you don't know how much phosphate is loosely bound to it and the rock that will cause trouble later. You risk contributing too much to the dissolved organic levels and unacceptable phosphate levels in the tank if you don't treat the dead/dried rock.

I would "cook" the rock a long time before I used it. That means a long soak in salt water... in something other than your display tank... with a power head running, some water changes, and possibly using lanthanum chloride to help treat phosphate issues.