Of course not. 10 minutes is the mean, not the median. The median (the point where 50% are higher and 50% are lower) is 6 minutes and 56 seconds. It should be expected that the median will be much smaller than the mean because there is a lower bound to the block time (zero) but no upper bound. It is possible to have a block time to be 20 minutes longer than average, but it is obviously not possible for the block time to be 20 minutes shorter than average (because it would be less than zero). Thus there a few very long block times that aren't (and can't possibly be) matched by very short block times, and this skews the average.