There's also the concept that the Xbone is central to a unified media presence; it's a better way to watch cable TV, or subscribe to various internet services... and in Japan, that's not yet the future. We didn't get mail-back DVD envelopes until last year, and the streaming services are not yet present. Hulu.jp is making a pretty good stab of it, and each of the ISPs is making their own bid at having IPTV in the home, but adoption is not widespread, and none of it is as dirt simple as having an AppleTV/Roku/Xbox with app and logging in.
These ISPs are providing Roku-sized boxes, but I'm guessing it is an attempt to wring cable-like fees out of the captive island audience of consumers.
The Xbone is likely building on the streaming/service based environment which has arisen in NA, and would not have any traction in getting Japanese media providers to cooperate with them. It would be an utterly pointless struggle.