He make a good point about there being no studies proving "10x programmer". I don't think it is something you can prove with a study. You would first have to define the metric you are measuring. Lines of Code per minute? Time it takes to build a basic fizzbuzz, web app, compiler? Standardized test?

Once you defined a measurement people could study for it. Someone who has memorized a gzip function is going to make a compressor 100x better than I am going to from scratch.