If the grades are impressive you should be proactive and send it.
Repeat -- If USNA wants them, they will ask for them. Further, as a practical matter, if mid term grades are "impressive" enough to make a difference, the candidate may not be competitive anyway. "A's" are an expectation, so wouldn't expect that to add to the application.
@Old Navy BGO …. I agree with all of your points with the exception of the "A's" being the expectation. I would also say that it wouldn't hurt for a candidate to send their Mid-Term Transcript if they are Proud of what they have accomplished while still awaiting an Appointment. It should make the Candidate feel better for trying …. You can't succeed unless you try.
Now about Grades vs. Challenging Subjects and Busy Schedules: My wife and I have never been concerned about our DDs grades, and they have never been all As …. and she has an Appointment …. She is a very Busy Bee though -- all the typical stuff, JROTC (PT Team), Community Service, 4-H, Multi-sport, Piano Guild since age 6, Cello Orchestra, and Performs alongside my wife (also the church pianist) on many Sundays. So her schedule is never empty.
I think a Challenging HS Schedule (Calculus, Physics, Chemistry all before the Senior year) with a Busy extra-curricular involvement can make a huge difference. And some Kids win a lot of Awards (like my daughter) for their ability to write and communicate affectively. This doesn't get enough attention. Also, the whole SAT/ACT super scoring thing is over done, and abused. For some kids and parents, it is a sport …. When our daughter took the test for the first time as a Junior in May 2018, she happened to score above the 90% in all categories. My wife and I told her that she was done …. There is No point in taking the Test again. It is meaningless at that point just to squeak out that little tiny bit …. Move on.
I had no idea what our daughters class rank was all throughout HS, and I didn't care, because she was happy, and that makes us happy …. I was a little startled when she told us about it while she was working to complete her USNA application over the summer. In 1980 when I graduated HS, I had a lower GPA than hers and graduated top 3 or 4% in my class, and went on to an undergrad at UVA and PhD at VT .... Personally, I think the whole GPA thing for a lot of our kids is so unhealthy. I don't think its the best measure of success. I think balance, staying busy, and doing things even if you think you are not capable are much more important.
Just because a kid didn't get the top grades in Calculus, Physics, Chemistry in HS, doesn't mean that they will fail at them in College. By then, they have a few years of maturity behind them. And that makes all the difference.