All I know is that you must never "reuse" an email address for another YouTube account because, even if not "correctly" linked (in that it shows UP on the Google account's dashboard), it will "oust" the original/older account to the point of no return.  So- if you open a new YouTube account first create a new Google account with an unused email address (you can create one specifically) before you go onto making a YouTube account.  :)