People put to much stock into a players ranking coming out of high school. Sometimes it carries over into the next level, but often it does not. Some players if not peaked have almost reached their potential in high school. In today's WBB world when players play year-round from an early age and engage personal trainers to work on individual skills, there is often not much left to develop in that respect by the time they even get to college except physical development and working within a team concept.
Just because Walker and Williams #1 rated and elite in high school, does not mean they will be that in college. I know that the posters on the Boneyard have been disappointed in their expectations of Walker. They also had high expectations from Williams at the start of last season based on her rating and showing in the McD AA game. No player in the 18 class established themselves as #1 for the four years they were rated. It was a case of musical chairs. Williams just ended up at the top at the end. There really were no standouts throughout.
I suspect that Williams has little upside left. She is a solid and smart player who knows when to take advantage of opportunities as they present themselves on the court. She is not, however, a go-to player who can consistently create her own shot. She does not possess the superior athleticism for that. The key is that she is subpar on defense and admits that she needs to get quicker. Footspeed is the key to playing good defense and you can only improve footspeed so much. That same footspeed is what creates a quick first step and is essential if you are not very fast for creating shots off the dribble. A good defender can always shut you down. While Westbrook is not as technically sound as Williams, she because of her quickness still has a bigger undeveloped upside. Unlike athleticism, you can increase your BB skills and court awareness.