Just to answer the question, many if not all manufacturers underrate their vehicles in published performance stats.
This makes sense from a legal stand-point. If a manufacturer said you could do 0-60 in 7.1 seconds (at the track, with a professional driver) and you could only do 7.9, people would sue them for overrating performance.
No one in their right mind finds themselves insulted that their vehicle performs better than published stats.
Even Corvette in the 60's was underrated in published horsepower. I believe the 427ci motor was rated at 450HP, but they would dyno straight off the dealer showroom at over 500HP without being specially tuned or anything.
Mazda bought back RX8's because overstated HP numbers.