It doesn't claim that. It says that 25% of young men and 45% of young women are repulsed by sexual contact. That means that 75% of men and 55% of women are still open to it (and, presumably, having it).

I'd bet that if you looked at an American college campus, you'd find similar behavioral statistics, due to the declining ability of young Americans to form intimate relationships (which may not be their fault). Casual sex doesn't fit most people. Many people (including most men) can't get it and many (including most women) don't want it. Only about 50-60% participate in the casual market even once, and half of those end up wishing they hadn't.

Still, a 35% sexlessness rate among people in their 20s means that something is wrong. It doesn't mean that people have stopped having sex (65% are) but it's still a sign of something unhealthy. I don't take those numbers (which are probably not very different from those in the West) to indicate voluntary disinterest, but artifacts of undue stress.

When the cause of the sexlessness (which is not just a Japanese problem) is unnecessary corporate stress, it's worth looking for solutions.