What does it affect then? if the rattling is just a nuisance and not causing damage, why fix it?
Because the locking pins in the phasers have failed, causing them to "park" improperly on engine shutdown. When you start the engine and the phasers receive oil pressure, they rattle. This issue has existed since cam phasing was invented, but unfortunately these engines received defective phasers from the parts supplier which has caused the issue we're seeing. It can't really get worse once the phasers stop parking, but why would you want the issue?
I guess I don't understand. If there is a TSB issued for this, wouldn't that mean there was some kind of problem it causes for the engine?
From what you are saying, it sounds like you want people to disregard the sound and all will be fine. Is that what you mean? I had mine replaced and the service people said that it needed fixed right away so I didn't lose the timing chain too. My repair did not get a new chain.
Certainly it is a problem, hence the TSB. The cam phasers don't park on their locking pins properly on engine shutdown, which causes a rattle noise on a cold start when oil pressure reaches the phaser cavities. Please read the SSM I posted...I am not saying to "disregard the sound", I am saying that the SSM indicates that there will not be any negative long term durability affects on the engine while owners wait for parts to be ordered and fullfilled. The timing chain is NOT the problem nor does it need to be replaced, the service advisor that told you it needed to be fixed right away or you'd "lose the timing chain" was misinformed.