That doesn't mean much. He was hired as an assistant professor in 2003. He was made an associate professor in 2004. He left Stanford in 2011. Probably the earliest he could have been made a full professor is in 2009 or 2010. My guess is that he already knew he was leaving by the time 2009 rolled around. The department isn't going to make someone a full professor if they plan on leaving in a year or two.