Echoing what
@OldRetSWO said.
Summer programs are part of USNA's strategic outreach (In BGO training, all summer programs are in the strategic outreach chapter). Attending or not attending has no bearing on potential applicant admission. Between plebe summer, multiple sport camps, STEM, NASS, sailing camps, there simply are not enough seats/beds for every kid who applies for summer programs.
Not being invited/accepted to one, has nothing to do with whether or not you will be a competitive applicant for admissions.
DS did apply for STEM, didn't get in. The following year, he applied, and noted in his application he was in a very rural area with limited STEM opportunities. He was selected and loved it. He applied for NASS, got denied. Had no bearing on his future candidacy. He commissions on the 24th.
Don't overthink the competition part of this. You will drive yourself insane. Your DS can put his best application forward, do the same for every nomination source he is qualified for, and keep kicking butt. He should only focus on what is within his control. His competition, what admissions is trying to piece together for the future Class of 2029 are things that are out of his control.