Off topic, but this is the dumbest reason ever to refuse a warranty claim. You can drive all day long at 3000 rpm without overheating the vehicle as long as you let the turbo cool off, especially at 80 mph where a) there are tons of airflow. b) the throttle application is actually very low, meaning that the load on the engine is light and there are very little fuel being used. Like everyone else said, I would definitely fight it back and ask them to prove that this is abnormal behaviour.
As far as telemetry, Mazda could also just save all that data on vehicle, and have the dealer extract it when the vehicle is in the shop. I expect that is pretty much what all cars do. I am not a fan of it either, but i am sure that is what most connected services do (Hello OnStar)
At least in Canada, Mazda is fairly open about the collection of data. And allows you to disable it (altough it is on by default). See the link below.
We provide you with choices about what data and information you share with us and how it is used. Click here to learn about our data security and protection.
“Among the many ways you can control the use of your data, you can: review and update your information that’s shared with us through the MyMazda app; unsubscribe from marketing emails; disable the collection of Vehicle Data from your Connected Vehicle;
cancel a Connected Services plan, plus other choices you can make regarding your personal information and data.”