If you ‘enable’ privacy, then it does as the help says – it hides the details of living people – in accordance with your subsequent settings.
If you ‘disable’ privacy, then the details of living people are NOT hidden, regardless of any subsequent / other privacy setting you might try to use. In other words, there is no privacy.
I have living people set to show to visitors already
Really? I’d be surprised if you have. I can’t think of any such setting. Are you confusing it with “Show dead people”, the setting below “Privacy options”.