The Nikkei is sometimes incorrect about technical details (it's a financial paper after all), and the mention of EPUB on Kindle could be their misunderstanding

The Nikkei is sometimes incorrect about technical details (it's a financial paper after all), and the mention of EPUB on Kindle could be their misunderstanding or just a wild speculation, which is their another trait. The original article online appears to be behind the pay wall, and I couldn't find relevant article on paper, so this is just a guess...