Agreed. It is quite naive for athletes and their families to think that the coach who recruits them will be there when they graduate.
Of the coaches in the link below, exactly half have been hired in the last three years! 27 in 2019, 20 in 2018, 18 in 2017.
Only 37 were hired in 2015 or earlier. Only 26 were hired in 2013 or earlier, but exactly half of them (13) were hired in 2008 or earlier. I
In other words, if the coach who is recruiting you has already been there for a few years, but less than 10, watch out!
P.S. And that is the head coaches who are the most stable. To expect that an assistant coach will stay is downright dumb.