We only void warr on parts directly Related ie I have a customer with 2.5 wheel spacers so I had to inform him that we would no longer offer him warr on his wheel bearings. We did give him a set before cutting him off.
It's a shame that things went this way. I see a lot of bullshit go down at dealerships. I also see a lot of goodwill given out to people so do and don't deserve it. Often we will go goodwill to settle out a unhappy client they pay labour we cover parts and yes they come out of a fund we are allotted. It's not just a cash grab.
Still try another shop before you finalize things. See if he indeed put the info onto mitsu system.