Hi Mark and welcome to the site. He has very nice athleticism, fluidity and a good natural throwing motion, particularly for a tall freshman. There is certainly lots of potential there and the best thing you can do is settle on a good pitching instructor and be careful about taking in a wide range of conflicting opinions from us folks taking a quick peek at him on youtube. That said, I'll go against my advice and throw out a few opinions any way
You will find (if you haven't already) there are more than one "correct" sets of pitching mechanics taught... drop 'n drive, tall 'n fall, short stride, long stride, etc. Keep this in mind when matching your son with an instructor.
I do agree with some of the previous observations regarding hip/shoulder separation but I would point to something else as a possible cause. Look at the 17 second mark. His plant foot is not parallel with the mound but instead, the toes are toward 2b and heel is closer to home plate. At leg lift, his plant knee is well outside of his plant foot. This combination causes his back side to leak out to the left and prevents a good torqued rotation.