My experience is that the higher end bikes or racing bikes are more prone to have a mix of components. I guess people who bought these type of bikes new were the type that wanted to make theirs special and would add or change things after a race or a few rides. When I restored or refurbished my ItalVega last year , it had some interesting , period correct components that told me someone was either a racer or just wanted to make a good bike even better. The most interesting was the seat post , a Zeus Competition while the cranks and other parts were Campy.