I'll bet its a complete revamp. I DON"T think that specific one was source 2, but a beta version (as stated on that page) of the standard engine update.
I think the next engine will be just like the current, like having a supermodel come up to you in the bar, you take her out for a drink, then find out she has had 3 kids, her career has failed, and she has STD's.
They really messed up with Steam, IMHO.