I hope I can help some of you understand through my own experiences. Firstly I do have kids that have made NPP/NITP and yes they are in that tall category mentioned, however they have always displayed a strong work ethic and a high skill set among their peers so yes again they tend to stand out.
They have also have their disappointments over the years, not being selected at under 14 academy or not making a state team as a bottom age player or not making a national team for various reasons.
No matter the outcome, there is one thing that stands out in my mind and that is the character of the kid (and parents for mind). Your journey, like mine, will have its ups and downs, your true character will come out along the way.
For us it has always been to ask politely what needs to improve, then go back and work harder. It has always been to adopt a positive attitude and not take anything for granted.
Injuries, illness, maturity, school work, growth spurts, distractions, peer groups, effort, desire, attitude and potential must all be considered by coaches, selectors and families as they support the athlete who is trying out for an elite level of competition, no matter the sport!
Take it from someone who has been there in every aspect of these programs (other than in the coaching/selection phase), they are looking for those who have the potential to sustain elite levels of training, elite levels of skill and elite levels of character.
Kids up to under 18 age group can still be late bloomers, so it isn't over for any kid with potential and the character to stay with it. Many examples exist today of kids who only came into their own at or over the age of 18. So don't give up on them and stay positive, NITP isn't for everyone and it isn't 'Making It', it is just another step for some that has come at the right time for them...