I dont think he WANTS to strip the stain, i think he is worried that the hypo will strip some of the stain out, and he doesnt want that to happen. He just wants to clean it.
Just to let you know Roger I did a simple pressure clean with water, it was fine, removed most of the built up algae etc but it did need stripping, which I didn't have time for. Anyway simple clean, customer happy, and got paid. Not really my thing decking, if the picture thingy worked i'd upload some before and after shots.