We have no way of knowing which of the sample 10 photos is most representative of the most optimum focus his particular camera and lens combination is capable of producing.
There are 10 images presented, 6 of which are similarly sharp, 4 of which are not as sharp (and one of those 4 is a blurry mess). Are you suggesting that the 6 similarly sharp images are all random misses from optimum focus that happened to coincide in terms of sharpness? I think Friar William of Occam would disagree with you.
Precision and accuracy are independent, although they may certainly appear to be related, depending on the resolution of the measurement method relative to the accuracy and precision of the system being tested.
I certainly agree that it's premature to base an overall conclusion about the 50A's AF perfromance on issues found by two review sites, each testing one lens.
In this instance of trying to measure precision, the lens could be front or rear focused. So the to and fro of the lens at its furthest point might look like a mess, but if the lens were afma'd correctly, the focus could be within three units of the proper focus... making all of the shots tolerable versus some of the shots being as many as six units of auto focus off.
We want to make sure we are only identifying its precision... not its accuracy which is why afma is a requirement.