Agreed! Once you’re in the 1st decile or better - in your case even the top 5% - the detailed numeric standing means very little, in my opinion.
The same person, taking the same classes, can be #1 in one year, or #4 in another year - just based on whoever else happened to be in the same grade. That doesn’t change who YOU are and how well you might be a good fit for a certain college.
Also, high schools typically use the entire transcript from 4 years to calculate rank - including A+ received in all kind of elective and other “filler” classes. The resulting ranking is of little relevance to colleges because there’s no way to compare against other high schools.
So they likely will pick out various core subjects, consider the rigor of those courses, and the results there, to assess how well a student did academically, compared with applicants attending similar competitive high schools.
You just need to realize how “thin” the air is at the top. Everyone else applying will have comparable grades, scores, ranks etc. and the admissions may often seem more like the result of rolling dice (not that they are), because there a plenty of cases every year where the numerically top students are not admitted, while seemingly “long shot” applicants are offered admission.