For OP, you described your son as a “very positive person,” positive he would get into at least 1 SA.
A wise boss once told me that having too much of a good trait can also be a leadership flaw in certain settings. Being positive is good for an officer to be, because the troops watch leaders very carefully, so being confident and upbeat in the face of challenges sets the tone. Being so positive that alternate plans are not created, always a prudent move of the adaptive junior officer who must be ready to meet a challenge no matter how it twists and turns, shows that the “too much” positivity encumbered the leadership in a negative way. Rich essay material!
I am hoping the other SAs deliver better news, and while painful, your son is learning a valuable leadership lesson.
Let us know how it goes.