I didn't really understand that this feature created a new post until this evening when I used it for the first time. I thought that it simply allowed you to share one post to multiple communities
It has been a common error, and unless called out, one might not realize at first what has happened.
but I think that there needs to be some way to post to more than one community without replicating a post developed in the future.
I think so too, and I think that it will happen. This feature is a bit different as it allows you for example to crosspost the work of a poet you find into a poetry community they didn't know existed - and reward them. It is pretty powerful.