Justin, who we all love, has 2 seperate videos with the following explanations:
This is a Cm7b5 with a 5th string root
at 8:38
This is a C9 with a 6th string root
at 5:05
By this logic, the Cm7b5 is also an A#9, and the C9 is also an Em7b5. He does not reference the alternate way...