I have also noticed the lack of mention of that, which likely is related to the fact DQX isn't available outside Japan. But it's still worrisome because two-thirds of the games involved have Western releases. And the internet being the internet, non-Japanese players do know this stuff is coming.
If participation requires playing all three games... then yes, it is going to be JP-only, and that is a great shame. I do so love DQ slimes...
