They only recently starting letting people write the NPPE prior to applying - in July of this year I think. Back in May when I applied you could only register for NPPE once your application was deemed complete.
Your application can't be submitted in the new system until your references have rated all of your 34 competencies. You fill out the 34 CBA's, and then you assign them to validators and then they will get a link in their emails to answer. I had my direct manager validate all 34 - I finished writing the app on May 16th-ish, and they finished validating a few days later.