The 10GHz part is the most doubtful in that comment. When you consider what speed they were at in 2007, there was no reason to believe they would get that astronomically fast in just 3 years. Hell, it would still be an astronomical achievement even 3 years from NOW!
Except development of CryEngine 2 and the game likely started around late 2004 if not basically around the release of Far Cry in March 2004. Around that time Intel was teasing the successor to the Pentium 4
being clocked really fast and boasting they could get to 10 GHz by 2011.
Even though Intel announced plans to cancel that development in mid 2004, it wasn't really drilled into the mindset of developers yet that multi-core was going to be the future and even if it was, it'd be a while before enough people had multi-core chips to even consider developing around it. So most developers went for the assumption that single core processors or reliance on a single core (after all, if you had a dual-core processor, you could just hog one core and the other would be fine to take care of other tasks) would remain dominant.
It really wasn't until the 2010s did developers finally start embracing designing game engines with decent multi-core support.
It's also possible that Crysis is either poorly optimized or using new algorithms that haven't been optimized around yet. Notably it was one of the first games to use SSAO.