Is “In official history, Wei Zheng was a prime minister, and there is no matter of him beheading the Dragon King in a dream” true?

The official history "Old Book of Tang" records that Wei Zheng was a famous upright minister and chancellor during Emperor Taizong's reign, stating: "贞观三年，迁秘书监，参预朝政。" (Old Book of Tang, Biography of Wei Zheng). However, in Chapter 10 of "Journey to the West", he becomes a remarkable figure who also serves as the official of the human realm, able to execute the Jing River Dragon King in a dream by heavenly decree.