Females are socially inept
Females are just as socially inept as males when it comes to interpreting body language and other social cues.
It is often said that women are more socially savvy and much better than men at reading social situations. But the reason it might appear this way is because in this culture women (as a whole) take virtually no risks and always play on the safe side. They are so hell-bent on getting society's approval that they go to all these extra lengths to make sure that they don't do anything "wrong". So as a result, we never or rarely see women make a fool of themselves. Of course not; they don't do anything! Men do all the work, take all the risks, get rejected, and then (many of us) go back to the drawing board to "up our game". And the PUA is merely an extreme case of this.
White knights read too deeply into female body language. Here is an example of a comment by a white knight:
The rejections are your TEACHER AND FEEDBACK, imo. They teach you the subtle signs girls show when they don't like you (you learn to see through friendliness which SO MANY even normal guys can't do) and the not so subtle signs they show when they do like you. It's such a game of making sure to make your intentions clear non-verbally while seeing what the girl will let you get away with. All these subtle little moves are made.