I was alive when the novus ordo was introduced, and although I was not Catholic yet, my mom's family was. I remember it was a major subject for discussion in our family.
The NOM was introduced in 1970, and made mandatory in I think 1974. However, from the end of V2 to 1970, some slight changes were being experimented with. Actually the changes began before V2, with the "dialogue mass", which encouraged the people to say the server's parts, similar to protestant services, and unlike traditional RC and traditional Eastern Orthodox liturgies.
Hence, Padre Pio might have been aware of the slight changes before the formal introduction of the NOM, but as for actually saying the NOM, no he didn't.