The other question is, if they did see it, why would they care?
The service department of your dealership isn't owned by GM, it's owned by your dealer, as a franchise. When they do a repair, they generate billable hours, which go either to you or to GM. If they deny your warranty they have to A) argue with you about it and B) risk losing you as a customer, not only will you probably buy your next car elsewhere, but you also won't keep coming in with this one generating billable hours. Meanwhile, if GM pays, well, GM is used to paying and they built your repairs into the price of the car.
Not to say some service departments won't gig you for every little thing they can, but just to say it isn't actually in their best interest to do so, so Most of them aren't going to look too closely.
Then you have people like me, who bring in a list of every mod and tell the service manager up front I don't expect them to pay for anything -I- broke, just for OEM parts that aren't my fault. If I can get coverage (and I have) then I'm pretty sure you can when all you have is the tune Chevy should have given you in the first place.