I guess I look at it in simpler terms...why take your top hand off? What is the purpose/benefit behind it?
When I work with my hitters I always encourage them to leave the top hand on all the way through the swing. The main reason is in watching video of them swinging there seemed to be a lot of early release of the hand, especially on off speed pitches. It was hard for some of them to work fight the urge to finish one-handed and some never did, but the ones that did work on it found better barrel control and more power.
I think there is a massive amount of evidence that shows the bolded to be incorrect, either method can be very good. I don't doubt your observations but I would guess it is a matter of the sample size being too small.