Drafting players out of high school is not an exact science. The LA Angels have had some good success in seeing those diamonds in the rough such as Mike Trout, Jo Adell, and Brandon Marsh to name a few. Justin Upton also came straight out of high school and was in the majors in two seasons just as Mike Trout was for the Angels, but they are the exception rather than the norm. So Angels prospect Nonie Williams has the odds stacked against him to a point.
Cam Bedrosian and Ty Buttrey took five and eight years respectively to reach the majors after being drafted out of high school.