Is that a subtle brag?
Most countires in the world do not field militaries large enough to make Colonel Generals or Field Marshals neccessary.
Basically when such a role ever comes up, a four star general takes up the assignment. At the end of World War II, some American generals were given five stars, but apparently this was because they had to deal with a lot of Soviet and European counterparts who held ranks that exceeded any American rank. So it was really politics.
The Japanese Self Defense Force is hardly big enough to require a five star general for any practical reason.