Yes, the whole thing is a PR stunt. So what. It made me smile
The summary is a summary of a summary. Figure 2 in the original report is much more informative. The majority of the highest scoring people use Firefox (35%) or Chrome (20%). The majority of the lowest scoring people use IE7 (35%) or IE9 (20%). Opera and ChromeFrame are not used by people scoring lower than average.
As for correlations I would guess the following:
IE7 -> low score.
Firefox -> average to high score.
Opera and ChromeFrame and Camino -> high score.
Safari -> not much correlation at all.
Other IEs -> not much correlation, tendency to lower scores.
Anyways, it's nothing but a joke.