Yup, just checked too. That's his first 10' on cam for sure. It is 25 June 2009.
This is his friend Pat Kingsley introducing him to the yt dunk community 15 days earlier:
https://www.youtube.com/watch?v=H9LeaVxKAKgHe says he can dunk 10' in the description.
I do remember that specific video you are saying, can't find it. It was a couple of months before the 10' dunk, Rim was 9'9'' or 9'10'', he could dunk it rather good but it made you wonder if he could dunk 10'. I remember very clear that i didn't expect at all when i saw that 10' lob.
Whatever, he is #1 right now imho. Word , between all those beasts/legends out there, currently i feel he is the best!