The amount of misinformation on this topic is unreal. Nothing "voids" your warranty. Adding a flash tune (APR etc.) to your car *may* cause issues with powertrain warranty claims. VW gets to make that call, not your dealer, regardless of what they tell you. APR Plus is a third-party warranty that will cover what VW won't (b/c you have tuned your car), it obviously has stipulations. Read the warranty 101 post that is sticky'd on this page. Example - I have a tune and had no issue getting an HVAC issue covered under the warranty. If I blow my DSG, that may not get covered. You can not modify your car and expect VW to cover everything, period. If you can't afford to deal with a costly repair warranty claim that will be denied, don't tune your car.
This is what my post was inferring, hoping the OP would research APR+ and see it's a third party