Tire Tread/belt problems of the 2002 Lexus SC430

About a year ago I bought a 2002 Lexus SC 430 hardtop convertible. The tires had to be replaced at 11,000 miles because the inside tread was cupping and making horrendous growling and vibration noise. I called Lexus and the factory rep came out and talked to me and said they all do the same thing and the problem can't be fixed. I could not see the problem and the tires looked perfect until you removed them and examined them. My worry, apart from the $2,000. 00 to replace the tires is that the vibration of the tire at high speed could cause a failure. I feel that Lexus knowingly sold a car with an inherent defect in the steering which could cause serious harm if not fixed. Lexus gave me a new set of tires but I don't believe they should get a pass on this.