Why is the revelation of grace doctrine called a Pauline revelation?
It is called a Pauline revelation because God revealed the mysteries of grace doctrine directly to Paul during three years of private training. These truths concerning the church and body of Christ were not in the Old Testament or Gospels; they had been kept secret in God's mind until Paul received them.
Les teaches that after Saul's conversion, God took him out of Damascus, likely down to Mount Sinai, the same mountain where He gave Moses the Law, and for three years gave him a private, solitary seminary training. There God revealed to Paul the mysteries, and these mysteries become the whole sphere of grace doctrine. Les emphasizes that nothing of the church is found in the Old Testament and nothing of the body of Christ in the Gospels; it is strictly a Pauline revelation. Paul constantly appeals that we recognize it was to him these revelations of grace doctrine were revealed, and that up until that time it had been kept secret, hid in the mind of God.