I did some googling and polite emailing and received a response from Dr. Freedman about his procedure vs. HiCy. I'll summarize what he said since he has a confidentiality warning on his email, most of which Lyon hit upon already.
First off, the ASTC is a much more potent version of HiCy so the stem cell transplant is seen as required for patient survival. The benefit of an even more potent chemo treatment is the chance of destroying whatever disease causing cells are in the immune system and bone marrow. (If HiCy is rebooting, ASTC would be reformat and reinstall.)
There is also potential wildcard benefit in the stem cells renewing the immune system, blood cells, and brain cells.
my 2 cents: the only way these 2 procedures will be teased apart is with more trials and long term follow-up.