I have one Fender birdseye neck that loves to twist itself at random. Birdseye is, so I've been told, one of the more unstable grain structures of maple. My personal experience working with flame maple and straight grain rock maple also shows curly maple has a tendency to warp after it has been cut even when properly dried. My guess is PRS is uncompromising when it comes to wood selection and probably does not hesitate to scrap a neck going bad for a good one. On the original subject, I don't like the way maple looks on set-neck guitars. I'm more of a rosewood guy.