The creation is. In order to participate, all should be able to, no?
Here it’s just about interpersonal privacy. I don’t think discourse does implement any privacy-preserving tech. Probably it’s all stored in the server. But as an admin I can’t get access to that info through the UI. Probably only on the back-end.
So assume privacy from all other users users, but not from the back-end.
Note: the poll creator is the one who selects if the votes are public or not. When they are public I’m guessing it shows a note setting the privacy expectations.