My April-made 2001 makes what sounds like a valvetrain rattle on hot starts, but doesn't seem to have the cold-start knock.
About 3000 miles into the last OCI, a louder knock developed on cold startup. I added 6 ounces of LC20 (first use in this engine) and the sound went away within 1000 miles.
While my Chevy so far doesn't seem to be built "Like a Knock," I have been chasing an ignition ping since about 15,000 miles. IF the piston slap is caused by carbon, maybe it's been kept away with all the FP60, Techron, Redline SI-1, and Regane I have used to try keeping the chambers clean.
It's hard to know what the truth is with this problem. First GM changed pistons for some people who really complained (or maybe that was second), then they attributed the knock to carbon and did top-end treatments, then they redesigned the pistons. Then, miraculously, they discovered that the noise is normal, nothing to worry about, won't hurt anything, etc. At least they must be saving money on customer relations/warranty denial training, because service writers read me the same script every time I mentioned an abnormal amount of pinging.