It isn't even proven that the difference is genetic. There should be a study where they take Jewish kids that are raised in non-jewish families and look for the difference, then they should take non-jewish kids who were raised in a jewish families as jews and look for difference, even then it would not prove. For better measure they should take identical twins both jewish and non-jewish where one of the twin is raised as a jew and other as not jew. Even then they should take into account which environment they were in during prenatal period, jewish or non-jewish. Since these strict requirements are unrealistic to ever be achieved I view those types of arguments as more speculations than anything else. It is not a secret that even many scientists often fail to understand statistical data correctly, and in these kind of studies in particular there may even be certain motivation to project data at a certain "angle" to look it more like you want it to look.