It’s an interesting thing about federation between platforms - everything gets federated, even the platform-specific stuff that may be irrelevant elsewhere
Only on request though! The only reason this post is showing here is because they specifically tagged the !newzealand community. It works the same way between lemmy servers, our All feed has content from other instances, but only from communities that people on Lemmy.nz have subscribed to (with one little exception where we have a specific seeder account that is subscribed to a bunch of popular communities so we don’t miss out on popular stuff on other instances that no one has subscribed to).