What the middle-aged letter delivery man heard was real. There were two peaches; the one that was taken by the white crane was the Daoist. While he was an unusual object, after going through many challenges, he finally achieved enlightenment under Xuanmen.
His Mana however was not as deep as his elder brother, as ultimately he took in blood and flesh of living beings. The cumulation of Mana allowed him to go through the trial of thunder. One could imagine the level of Mana the elder brother possessed.