Actually, I did a little more research and it seems the HC used in their description is short for hydrocracked; in essence this oil is derived from a group 3 mineral base. To be considered a true synthetic, it would have to be formulated from either a group 4 or 5 base.
What I do find interesting however is LM's VI of 175 which is higher than most competing "full synthetic" 507 approved oils. Still, I wonder what a long term UOA will show with the LM. I've seen a few posted here and they look good, but I believe most were analyzed with less than 10,000 miles on the oil.
ETA: Found a video on Youtube that describes the differences between HC group III vs PAO group IV pretty well. Disclaimer: it's done by an Amsoil rep.
http://www.youtube.com/watch?v=DGirwUAMnDE