First and foremost, I think that a summary of one year's early signings is insufficient data to draw the conclusion that you made. However, assuming the conclusion is accurate, I think one contributing factor could be that the prevailing norm in Alabama has been for the H.S. player to play H.S. and then American Legion summer ball, with very few "showcase" teams on the scene, (such as the Bama Bombers).
The college season is a tight overlap with H.S. season, and so the coaches look to the summer showcase events and major tournaments for talent. This means that they are going to be seeing a lot of out-of-state talent more than once, whereas an in-state player playing Legion Ball is less likely to be at the large showcase events, and will be fortunate to be seen even once.
Interestingly enough, what I am seeing now is that the number of youth-age travel teams is increasing in our area (north Alabama), and I would not be surprised if that trend continues to provide more options vis-a-vis high-level travelling teams such as the Bama Bombers for talented HS junior and seniors to get seen. Then more Alabama players will be visible to the college coaches.
p.s. There are some H.S. coaches in Alabama who need to do a better job of promoting their players - thankfully my son's coach was not one of those! I've also heard far too many H.S. players with upward potential say "If I'm good enough they will find me." In this day and age that is a foolish statement - a lot of them don't get found because they don't do what it takes to promote themselves.
"seven days without bar-b-que makes one weak"