How could he have gotten a nomination that early too? I know for my MOC the deadline isn't till October.
Those eligible for Pres noms (which are non-competitive) and an LOA can receive their appointments very early.
In terms of NASS and how much it helps or doesn't help . . . first, read the sticky on the subject which goes into great detail. Below is a condensed version.
NOT attending NASS doesn't hurt you. Whether you aren't selected or whether you are selected and can't attend for some reason, it's not a negative.
NASS
can help a bit. If you attend and do really well, you can get a SMALL number of bonus points. The thought is that you performed well and also now have a better understanding of what USNA will be like.
However, be aware that there are MANY, MANY, MANY ways to earn bonus points. These include having a military parent, doing well on the CFA, being a team captain, having high SATs, having great grades, holding a job, being an Eagle Scout, being class president, being all-district in a sport, having a great teacher rec, having a great BGO rec, and on and on and on.
On the flip side, if you show up at NASS and are a negit (someone who doesn't put out, who complains constantly, etc.), attending NASS can actually hurt you.
And, as stated well by the above poster, everyone at USNA was a star in high school. The first thing you learn is that there are a heck of a lot of people smarter than you, faster than you, stronger than you, more organized than you, better at swimming than you, better at boxing than you, better at chemistry than you, better at sailing and shooting than you, better at memorizing rates than you . . . get the picture?