As vjkane will attest, that is a problem with a lot of JAXA missions--it is not clear when they are approved or just proposals. At least with NASA missions you know when something has approval to go into development (assuming that you know how to actually find that information). I think that the Japanese have a different approach to this kind of stuff. I don't know if it is cultural, or the way their bureaucracy works (two sides of the same coin).
I believe that all space agencies have formal processes for exploring, considering, approving, and developing missions. For me (and I think many on this forum), we have the web resources and language skills to understand and follow the process for NASA and ESA. For other space agencies, I just don't understand their formal approval processes and just going to their websites often doesn't help either because of language issues or the governments have policies of putting minimal information on websites.
Think of all of the mission studies that NASA does, of which only a tiny, tiny fraction of which will every be approved for development. The Uranus orbiter and atmospheric probe is an example. It is a prioritized mission concept for future flight (last Decadal Survey, statements by NASA managers, effort expended by NASA studying the mission), has had many concept studies, but at this time remains only a concept. To be approved, it will need to receive a top priority from the next Decadal Survey (beating out the return of samples from Mars, a Europa lander, two list only what I consider to be the top two among many contenders for this contest), be included in a President's budget plan, and be funded by Congress. This is a number of hurdles for a mission that NASA gives every indication of wanting to fly.
I believe that each space agency has a number of mission concepts that are in the same category as the Uranus mission. Hence the confusion of knowing what is an early idea, a desired mission, and an actual approved and funded mission.