1 in 2500 chance that any block a pool solves is 99.96% CDF or worse.  That is a fact.  Slush has solved just under 25,000 blocks.  Over an infinite number of samples of pools with 25,000 blocks solved, you would expect the mean number times the pool encountered a 99.96% CDF or worse block to be 10.

Now if you go through slush's history and find 20 times that there were 99.96% CDF (or worse) blocks, then you might have something.  Or maybe if you find that in the last 5000 rounds it has happened 5 times, you might have something.

Otherwise you're trying to claim something shouldn't happen when it clearly SHOULD and WILL happen multiple times in the lifetime of that particular pool.