GTK 3 macOS: Japanese keyboard schemes do not work correctly

Steps to reproduce

1. Have a very basic GTK 3 app with at least one entry.
2. Switch between the different japenese keyboard entries on macOS 13:
   1. Hiragana - Kana
   2. Katakana - Kana
   3. Hiragana - Romaji
   4. Katakana - Romaji
3. Enter text.

Current behavior

1. Hiragana - Kana works correctly
2. Katakana - Kana does not work correctly, instead entering characters of "Hiragana - Kana"
3. Both Romaji input schemes do not convert to Kana. Entering "kei" remains as "kei".

Expected outcome

With all input schemes the correct characters are entered.

The Romaji input schemes should normally convert to Kana automatically. Example: "ケ" is obtained by typing "ke", "イ" is obtained by typing "i"

Version information

GTK 3.24.38 on macOS 13.5.1 (Intel based)

Additional information

This bug does not occur with GTK 4. It seems to be exclusive to macOS.