You aren’t missing anything. Zachary K. Hubbard is a con artist and a pseudo intellectual. Ronald L. Hubbard is most likely who he based his name off of and Ronald L. Hubbard himself was a conman.
I heard Harry Greb got his powers from mysterious, reptilian forces. That's why there is no footage of him. To keep Boxing in the dark.
Sorry I didn't even mean to put that vid in the OP!! It's not a good intro video to it. Not the biggest fan of Hubbard myself. I think he's a HALF truther. Hubbard has had 19 channels removed from YouTube though. Most con artist are given a bigger platform. I don't agree with all of Hubbard but he has some heavy truths He's spot on every now & again man. This content is protected