People claim to know but the reality is, we have no idea. I suspect his frames are made by Wilson with custom flex and or composition - then send to Priority One to be made the same as each other in terms of weight, balance and handle.
His current frame is based on the K6.1 tour mould which, as shown in another lengthy thread, is ever so slightly different to the current BLX mould. Even then, some people even think this is merely a slight variation in the mould issue rather than an actual difference in design.
(moulds wear over prolonged use and therefore can spit out ever so slightly different end products - say with less defined corners etc... or perhaps the composition of paint changes too and has an effect in that area)