Chat messages have two translations, one for display and one for narration:

{
    "chat.type.text": "<%s> %s",
    "chat.type.text.narrate": "%s says %s"
}

Due to the text refactor in 22w16a, only the display text is used for both display and narration. In particular, the narrator says "author message" instead of "author says message".

This is caused by Minecraft checking whether the text itself is translatable, when due to the new class hierarchy, only the content can be translatable. Specifically (Yarn mappings:

public static Text replaceTranslationKey(Text text, String oldKey, String newKey) {
    if (text instanceof TranslatableTextContent && oldKey.equals(// ...
    }
}