I think they do it a lot more often than on Fridays. I’ve wondered if, combined with the hours, it had something to do with the death rate of company men in Japan.
https://www.bbc.com/news/business-39981997
My best bud who works in a certain prefecture away from Tokyo told me one story which he confirms to be truthful. About one of the big Jap companies sending their workers to the US subsidiary to learn our ways. I think it was Honda.
Once 5 PM struck, everyone packed their gear like clockwork. The Japanese dude continued to work, and was shocked why everyone left on the dot. His American co-workers had to explain to him that in America, work stops at 5. Over there, it is frowned upon to leave at 5 or 6 pm, depending on the company hours which they see as rude.