Indeed, the openssl test shows an even more surprising variation on 2.6.29 (although at least one person on the phoronix forum tried and failed to duplicate that result on another machine).
Phoronix has always come at their reporting from a "typical desktop user" perspective. This is both good and bad.
Good, because "will it make my single-threaded mp3 encoding faster?" is a question many people may well have. The answer is obvious if you know anything about kernel internals, but most people don't. Also, asking "obvious" questions sometimes leads to surprises (like the GraphicMagick result).
Of course, it is also bad. The author himself doesn't know that cpu-bound programs "shouldn't" speed up with just a change in kernels, so he doesn't stop and ask "why?" when they do. He also doesn't appear to know what mix of programs might provide more insight into the changes between kernel versions.
In many ways, it makes me think of the sorry state of mainstream science journalism. The facts may be reported accurately, but without context or analysis the reader is left to guess about the significance of those facts.