All responses are correct. If the question is: "Does going to Summer Seminar Provide you with MORE POINTS on your application towards receiving an appointment". The answer is 100% NO!!! Not at all.
However; that isn't the WHOLE ANSWER, OR QUESTION. Let me "Restate" the question.
"Do PEOPLE who attend Summer Seminar have a HIGHER percentage of acceptance to the academy than those who DON'T attend Summer Seminar"?
I would say with this, the answer is "POSSIBLY". But non of this is because of your board scores at admissions. The answer is "Psychological", which in turn causes "ACTION". In English: People who attend summer seminar tend to be more MOTIVATED when they come back. They are more EXCITED. As such, they tend to try harder on their applications. They tend to get their application done sooner. They tend to stay up on their teachers, admin, etc... to get their application done. They are motivated to stay in better contact with their ALO, get their CFA done, etc....
Also; as long as you APPLY for summer seminar, it will give you a slight edge on your nomination application and during your ALO interview. (Assuming you mention on these apps/interviews that you APPLIED to summer seminar.) It shows your MOC and ALO that you are motivated and truly interested in the academy, and not just applying for a "100% Free College Scholarship". Whether you went to summer seminar or not isn't what matters. The fact that you applied is what matters. It isn't your fault if you didn't get accepted.
But again; those who DO ATTEND summer seminar tend to be more highly motivated. They put more emphasis, attention to detail, blood/sweat/tears into their applications, communications, interviews, etc... (No, I don't have any UCLA Medical School Behavioral Science Stats that show the different in commitment). But I've seen and spoken with enough academy applicants who have and haven't attended summer seminar, and you can see the difference in attitude.