If you want to get technical. The entries don’t even HAVE to be public. I’ve never made that a rule or even “general policy”.
The problem is that if you *don’t* then people who want to read your writing can’t. Which is why as a standard you see everyone posting a public entry to allow the greatest number of potential readers to come check it out.
But as far as “Idol policy” goes – you can make it a locked post. Just keep in mind that people can’t support what they can’t see!!! I’m not really sure why anyone would sign up who only wanted their FL to read their entries though.
So I guess that’s a “yes” to the question and a “shrug” to the rest of it!