Sobers was recognized as a true all rounder when he became a fast medium bowler around the time of the 1960-61 W.I. tour of Australia. A year or so later he added chinamen and googlies to his repertoire. Virtually all of his achievements as a true all rounder occurred from this period onwards.
Frank Worrell is a much better example. He was initially a slow left arm bowler before he became a great batsman..