Bro that doesn't mean anything. Just like when the U.S. claimed they didn't know anything about 9/11 or which country was buying oil from ISIS. The West are masters of deception.
Pakistan has suggested a unified Muslim force since the 1970's. So why Saudi wait till now? With Pakistan's forces stretched from East, to Northwest, and to safeguard CPEC. And now Saudi wants a Muslim NATO for Yemen? Not for Soviet-Afghan war; not Indo-Pak wars; not Arab Spring; etc.
U.S. can act oblivious to Saudi's planned Muslim NATO all they want. But there's no way Saudi who throws tens of billions of $$$ away on overpriced Western military tech would ever go behind the U.S. back to create a Muslim NATO without consulting them first.
The U.S. most likely told their Saudi puppet to include Pakistan without it's permission, because they knew Pakistan wouldn't turn Saudi down. And now, since they have seen they were right, you can bet they're going to abuse there strangle hold over Pakistan.