Welcome to the forum!
Sorry to say that Audi Customer Services know precisely ZERO about any technical issues, and from my experience recently they just go and ask the dealership staff, as its actually them that have access to all the technical bulletins and service manuals etc. It is a very daft setup as you would expect them to be a littlre more clued up on some of the issues.
They seem reluctant to acknowledge there is a widespread problem with the turbo linkage, and are instead chosing to deal with each customer as and when the problem crops up (I guess to avoid widespread bad publicity?). It is hard to tell precisely how many cars are affected by it, as obviously a forum will give you a skewed sample.
Your best point of contact is now with your dealer, once they've witnessed the rattle they will be able to dig out the technical bulletin and get it sorted.