Obviously Salazar knows what he's doing technically and I don't think there's reason to question the validity of his workouts.
My concern with Cain is about the intensity of Salazar - he's shown with Rupp that he likes to get a runner young and develop long term, which worked wonderfully, but I think this is more dangerous with a young girl entering such an obsessive detailed environment. I think that it's very easy for girls (and I say this as a woman), especially talented ones, to be externally focused - to want to please coaches and adults rather than having an internal sense of satisfaction.
Being a pleaser and being a good obedient girl makes one initially very coachable, but it can also be very challenging for dealing with pressure - I think the athletes that do the best mentally are ones in it for themselves, with a strong sense of what they want to achieve on their own terms. If you want to please Daddy, and please Daddy substitute coach, and are in such an obsessive environment I think that can be very difficult emotionally to handle and lead to burn out.
I sort of think we'll see a year or two of spectacular performances and then trouble either eating-wise, or injury or burn out. I hope not, I want her to do well, but what I read about her dad seems like he's a very dominating Alpha male type (that doesn't mean he doesn't love or want the best for his daughter, but I get the sense of him being ambitious for her - unlike, say, Hasay's parents who seem to stay out of her training) suggests to me that she is a pleaser who is being pushed into this environment. I don't know if Alberto knows how to create a successful but balanced environment that allows a young girl to train at a high level while allowing her to develop a personality, interests and other outlets. I remember reading Rupp's blogs way back when he used to do entries on some running site, and it was literally nothing but run, eat, sleep, video game which obviously led to success, but was also a lifestyle totally focused on running with no other thought ever in his head. I don't know if women survive that kind of thing as well, and Alberto thus far hasn't really had success with women.