Feature Request: Tag new content

This post walks through how to tag new and existing posts. When I go to my community to replicate this, I can only add a tag to existing posts. I asked my CSM if this is the expected behavior, they said yes.

First of all, this seems absurd that there's still living documentation that is inaccurate. Second of all, one of the most beneficial reasons to enable tagging is so end-users can tag their own posts.

Why isn't this feature working as expected?