I think you may be overestimating the significance of SSAT scores for every single candidate. Yes, perhaps schools are chasing, or trying to maintain, an average so they “look good.” But on an individual basis candidates are admitted because they fill roles for the school.
I think, in person (online on CC it is super hard to tell), it is fairly obvious who will get in where. However!! I work with kids so I have a different perspective in making that statement and I have seen a lot of kids and a lot of kids’ work. In my experience parents are fairly deluded about their kids’ strengths. Like, really really really deluded.