I find it alarming that no one even seems to know what you are talking about. I wondered the same thing when I looked over the array of ratings for each pitcher.
I notice they have something called 'makeup', which is kind of like intangibles, I wonder if that is a factor, along with arm strength/accuracy. You could imagine patience may be a factor as well . . but it really seems like it should be it's own rating in a system so detailed as to track the quality of five different pitches for each pitcher.