What people fail to remember once you get outside the top 15 schools or so these coaches are leaving or getting fired all the time. They don't make that much avg $40k+ so for many its not a lifelong job. When kids were verbaling in 8th grade you were hoping the coach was there 5 years later. With the move to junior year there is a much better chance the coach that recruits your daughter will still be there.
From experience, coaches almost always honor the commits they inherit but then find ways to get out of and push or force inherited players out of the program to free up those scholarship slots year 2 and 3. They make it miserable for girls they don't want around
Not all scholarships are guaranteed for four years, plenty of schools it changes from year to year