That doesn't make sense. The MMO could run for another 10 years for all we know. Future expansions wouldn't be an obstacle to release it overseas, DLC is a viable solution.
They just don't think it's worth putting resources into it, whether it had a disclaimer or not. We can also say it's obviously not planned to get localised because all other games that would release globally were specifically mentioned, most if not all even simultaneous release.
SE doesn't want to put resources into it, perhaps they're hoping a platform holder like Nintendo to foot the bill, like they've done multiple times in the past (almost every DQ release is published by Nintendo outside of Japan, despite SE publishing them for other platforms in the case of DQXI and DQ Builders 2 for example).