ここって大文字じゃなくてハイフンつなぎじゃないとだめなんですか…？

[Pugma]

全然知りませんでした

[oribe1115]

この辺の話なのかな
https://www.kabanoki.net/4502/

私はVue詳しくないのでわかんないです

[oribe1115]

Like components and props, event names provide an automatic case transformation. Notice we emitted a camelCase event, but can listen for it using a kebab-cased listener in the parent. As with props casing, we recommend using kebab-cased event listeners in templates.
https://vuejs.org/guide/components/events.html#emitting-and-listening-to-events