I'm sure there are people in the Pentagon that can very accurately deduce what are capabilities are, let's give them a little credit, I mean, a lot of those men did get there based on their outstanding abilities and attention to detail.
But as I have said previously, military is only part of the equation, politics and general public matters. The Chinese saying of military actions should accommodate Politics is exactly this. During one of the campaigns against Japan, we could have eliminated a whole Japanese army, but instead, we let them go, because the national congress was gathering, and Chang needed a victory, the battle must end, so we let the rest escape and declared victory to the campaign.
The same is true in US, they don't want to hear the truth, the higher ups probably know it, but politics must come first, not because of personal reasons, but because politics is the more important of the two and nobody can have everything. I'm sure the white house is not made up of simpletons, and that is actually why they don't believe it, because they must look at this through every angle, and as it turns out, China must take a backseat to other more pressing matters.
It's not right or wrong, it's necessity.