I think some of you guys are missing the point. "False advertising" is when a company advertizes a certain benefit to be gained by the consumer from use of its product, such as, "Tide will get your clothes whiter than any other laundry detergent." If it doesn't, then you can claim it's a case of false advertising.
However, no specific claims of any consumer benefit is promised by the practice of pros using paintjobs. They never specifically claimed that if you bought a Head Flexpoint Radical, that you would be able to play tennis as well as Andre Agassi. Thus, no promises were unfulfilled because no promises of benefits from the use of the product were ever specifically made. In order for you to successfully sue Head in a court of law, you would have to prove that by using the retail racquet that you purchased, you can only play at best at a 4.0 level, but if you used Agassi's actual racquet, you would be able to play just as well as Agassi, since you were disappointed that after buying the racquet you were still not able to play as well as Agassi. Good luck proving that because you can't. However, if you bought the racquet just to look like Agassi, then that benefit has indeed been met because the retail racquet looks just like Agassi's racquet to anyone watching you play from a distance.
So I think people should just stop getting all bent out of shape over this paintjob issue. It's just marketing and they do it of course to sell more racquets. And if they didn't do it, they would sell far fewer racquets, and each racquet would cost twice as much as they do now. Do you guys want to pay that much more for tennis racquets?
I can't speak for US law, but your point doesn't hold in the UK. What are the laws on misleading shareholders in the US? Head claimed that there innovative technology was so good it helped Andre Agassi reach a Grand Slam final!