It should be standard in any nostr client that if you interact with a post, it broadcasts the post as well.
Discussion
Is this a different note type to “repost”?
No, just a function of how the client handles it when reposting.
It would make sense to me to have a distinct note type for deliberately “retweeting” a note, vs any reaction resulting in a “retweet”
We're not talking about retweeting.
Rebroadcasting just means that it is sent to all the relays you use, that way they don't have your reaction without the original event referenced.
The conversations tab of your feed on amethyst does this.