The difference for a majority of candidates is NOT the CFA. Each of the six events contribute to the 10%, with the majority of candidates falling into the normal range (hence the published averages of ACCEPTED candidates). The difference between an average score and an exceptional one (max or nearly so in every category) is around 2% of the total WCS. For the individuals winning districts and truly competing for a national wait list spot, it becomes even more inconsequential (1% or less) as the WCS to compete at that level far out shadows any improvement on the CFA.
That is like saying the difference between a ACT score of 30 vs 31 in inconsequential. 1-2% of the total score is big; particularly in a competitive district. If WP is deciding between two candidates, and one has 85% on the WCS, and the other with an 83%, which one would you like to be when there is only one spot? I know where I would like to be.
I can tell you that I was present when my son spoke with three different Admissions Regional Commanders at West Point last year, and all three confirmed the importance of a candidate distinguishing himself/herself with an excellent CFA, as opposed to "just passing", and that every single point on every ACT sub-score matters a lot, as most of these slots are very competitive, with closely scored candidates. The assessment of those RC's is very different from yours.
My son worked hard on everything, and ultimately received his appointment in mid January. He was told that, in the end, he was the "clear winner" of our district, and that it wasn't close, but when we first met with RC's the prior summer it was. The solid CFA mattered, and he was told it did, as did his improvements on the ACT. We were led to believe another candidate from our district was likely to still receive an appointment, as her application was also exceptional. In the meetings with RC's at WP, three out of three made a point to emphasize the importance of an excellent CFA score. If a candidate wishes to think otherwise, that is his/her prerogative, and perhaps the other elements of the whole candidate score are so high, or the competition is so low, that it wont matter. I would strongly advise not to take the CFA for granted though.
There are a number of ways to get in, and any one of them is good enough if you get the appointment. But All of the academies put a lot of emphasis on having well rounded kids, who have strong applications in terms of (1) academics, (2) leadership,
and (3) fitness. The CFA is the sole measuring stick on the third component, and contrary to what some here have said, it is not just a pass-fail test; it is scored and weighed for a reason. West point wants strong, fit cadets.