With the new update, this is achievable. Go to race, choose the pro championship and you now have to complete all levels again. Make sure to get gold on them all so you will make first in the championship. If you are struggling, you can make a front flip (good for 10 seconds stunt time) and as the time goes towards the timer, pause before it hits and restart. You will start with 10s stunt time. Hold B always... your guy will stunt any time he can, you won’t wreck and you will add lots of stunt time to help shave off seconds of your time for easier golds. Practice and good luck!!
Edit*- Apparently the update that made the leaderboards "local" haven't worked out too well. Everyones best guess is that you need to make the top 1000 on the leaderboard to have you score counted towards your progress. This achievement is once again considered buggy, or should be. Good luck and try to do this sooner than later, or message the guy on FB or Twitter, as he was responsive to the original issue.