Using that same example, you could consider American statistics misleading. US studies show that wage theft by corporations is a multi billion dollar a year industry. Things like that lead to underreporting of actual hours worked, hence, skewing statistics.

There were (or are) many workers work overtime without salary paid, they would be won't displayed in statistics.

There are a large number of workers in Japan. Even a mid-range percentage of a large number could be "so many".

By all means, the statistics could very well be wrong or misleading, but the number of stories you've heard isn't really evidence.

You cannot find any useful information about Japan in English. For some reason orientalism makes people abandon all common sense.