UPDATE: I changed the oil at 3000 miles after the flush. As part of it, I dropped the oil pan to check the timing chain to see if the guides were broken. They were. The plastic part of the chain guide was broken into tiny pieces at the bottom of my oil pan, hence the noise I was hearing on startup.
I didn't have time to get any pics, but now after having seen inside the engine with the oil pan off, I am no longer concerned about the engine having sludge problems. What I could see of the engine was very clean, only minor staining. However, not having seen the insides before the flush, I cannot conclude that the flush is responsible for the engine's clean condition.