Congratulations to your kiddo!
My D was selected as a semi finalist last year but did not progress. Never having done an asynchronous interview, she was completely thrown off by that format. In hindsight, I should have helped her more with preparation. She was well prepared for the interview itself, but not the asynchronous format. (She learned from it and did very well on other interviews.) I mention that so no one else makes that mistake!
As far as selection, of the kids at my D’s school who applied for Stamps, she was the only selected as a semifinalist. She did not have the highest GPA or test scores of that group. She did have excellent leadership and service experience and we believe that made her stand out.
Interestingly, she applied for Stamps at two schools and was selected as semifinalist at only one, arguably the more selective of the two. So it depends what that school’s Stamps committee is looking for.
Finally, since I’m not sharing a success story (haha), I’ll call in @itsgettingreal21 who was so helpful and whose amazing D has a success story (and continues to knock it out of the park!) Good luck to your kids!