I recently read the new biography of Padre Pio. There was a tremendous, long-running feud between Padre Pio and his supporters and others (going all the way up to the Vatican) who believed he was a fraud. Charges and counter-charges flew all over the place.
This was all hashed out in the cause for sainthood. It's not so much that the canonization closes the issue permanently, but that this was already dealt with.
What book did you read?