That was interesting, didn’t know they had an official romanji system and that it wasn’t the de facto standard.
This is basically just them officially giving up on the other system because no one uses it.
IIRC, it’s a holdover of a failed Meiji-era proposal to “modernise” Japanese by replacing its writing system with the Latin alphabet. (The one advantage it has over Hepburn is that it is unambiguous, and any Japanese text represented in it can be transliterated back into kana without guesswork.)
Hepburn makes the most sense to me as someone who uses both English and Japanese.
In Kunreishiki, rules like:
Long vowels are indicated by a circumflex accent: long o is written ô.
make no sense to me.
As an example, there are many possible variations for the famous baseball player 大谷翔平:
- OHTANI Shohei (I think this is his preference)
- OOTANI Shouhei
- ŌTANI Shōhei
- OTANI Syouhei
