The Bank of Japan needs a new plumbing unit.

By the time it announced the momentous overhaul of monetary policy last week, nobody cared. Everyone knew already what it would do, in excruciating detail.

That is because selective information disclosure has been one of the defining features of the bank since Gov. Kazuo Ueda took over last year. Since then, every major change has been reported in advance, in significant detail. But even by that unflattering standard, the level of spillage from the closely watched March meeting was scandalous.