All these years there were no strict rules that you have to finish authorized training and then get a VCP certification. You could go ahead and take up the certification and then finish the authorized training after which your certification would be complete. This was a wrong way of doing it but it was possible.
After lot of announcements that came out in VMworld 2013, VMware certification also went through a lot of changes. Now there are a whole set of associate level certifications that have been introduced and lot of changes have been made in the certification roadmap.
With all these changes, taking up a VMware certification also requires a authorization from VMware. Which makes it easy for VMware to evaluate if you satisfy the pre-requisite to take up the certification. As VMware and PearsonVUE have been integrated tightly in this matter, you can go ahead and book your certification only after you get authorized by VMware to take up the certification.
While a lot of talks are going on around if the authorized training really required before taking the exam, its not only compulsory that you have to take it up but you need to do it before registering for the certification.