Well in Japan the whole pop music scene is a farce - putting idols together just to grab the massive otaku market, and trying to make music in different genres (electro, hip hop, and now metal) just to differentiate because the girls are all underaged and unable to sing anyway.
Regardless of how vapid Japanese pop music is, I had the "metal-not-metal" argument enough times when I was a teenager to know that it's nothing more than an easy way to waste 30 minutes.
When did Metallica stop being metal? Was it "Metallica", "Load", or St. Anger? Were they ever metal? Does anyone over the age of 16 care? (the answer is yes).
I guess it goes from both ends. From what I understand, Marty Friedman (of Megadeth and Cacophony fame; there are few metal guitarists better than him) is now playing J-Pop, not even pretending to be metal.