So, we have: a single-sourced story from a news source that has in the past been an advocate of the removal of the U.S. base from Okinawa, an anonymous verification source (and thus unable to be contacted for independent verification), and a reprinting of the story by the BoAS, which has long changed its tune to keep itself as being seen as relevant.
I'm surprised that this story was even allowed to be printed, as single-sourced stories are usually laughed out of the editors' offices. Even in this case, if you allow 2 sources, usually you'd need hard evidence, not just hearsay.
How does the expression go? "Extraordinary claims require extraordinary evidence"? I don't see anything extraordinary here.