"The users who can participate in the wiki" is not clear and easy to understand

When you create a new wiki, at Step 2, you see this message: "The users who can participate in the wiki". At first view, the message seems to be clear, but after you create the wiki you:

1. you can't see the user on "User Directory" on the wiki's first page
2. you see the user just in Administartion - Users

So, the question is: what's the meaning of that message? The user will receive an invitation or a message that he was added on a wiki? The user will not appear on "User Directory"? He will appear just in Users on Administration?