The problem is that hes not just trying to cycle like you do in fresh water but to cure, there is major die off during the curing process and you end up with far more ammonium and nitrite than you need to cycle the aquarium, the excess nitrite and ammonium tend to kill off more of the critters on the live rock than would normally die and you then end up with more death and a longer curing process, in the ocean things get constant water changes, if we were to stock our tanks like the ocean is stocked it would be a 1 inch coral frag for every olympic sized swimming pool of salt water, water changes rarely hurt anything unless you are not paying attention to params or doing high percentage changes like 75% or 100%.
Also if by "chaetmorphia" you mean Chaetomorpha then you are correct about what I meant, I just thought the common name would be easier to find and remember. Also you don't have to wait till nitrites hit zero to add it, nitrite will have to be pretty high to kill it, andthe live rock will already have nitrifying bacteria colonies within it more than capable of handleing the load of a new aquarium, why you have such high ammonium and nitrite levels in a curing aquarium is that there is massive die off from the shipping process, the little bits of rotting plant and animal are too much for the system to handle and you must wait for the dieoff to be complete before the levels will fall, unless you are removing them by other means. Thats why you are advised to scrub off the dieoff with a soft bristled brush.