I dunno that the dealer really cares what you've done to your car. When I traded in my mk6 gti they made me sign something stating that I still had a cat converter. The sales manager literally said, if you did remove it I don't want to know about it. I signed it despite knowing there was no cat and the dealer knew my car was modified and that there was a highly likely chance it was gone. There wasn't even anything they did to verify it had a cat before I left.
Hell, I even signed over the mk6 to them and bought the new car on a saturday. I drove my mk6 home even though my name wasn't on it anymore and I spent my sunday putting some OEM parts back in. Monday morning I drove the gti back up there, and on the original tires that were at least 8-9 years old. I left my mk6 keys with the salesman and off I went. The mk6 was appraised with mods on it and they didn't even care to get a list of parts that I had planned on swapping back.
I think they just wanted to make the sale on the R bad enough that when it came to stuff like that they were just like yea go ahead do whatever you want. Granted, it was an older car that was definitely not going to be CPO'd. They didn't even attempt to sell it at their dealership, that thing got sent off to an auction I'm sure, so not quite the same scenario.
I tried telling them I replaced the tensioner and chain earlier this year too, it was a 2011 with about 80k miles, and they couldn't give a shit about that either.