Is “Who ultimately killed Luo Shixin?” true?

According to the Old Book of Tang, Biography of Luo Shixin, Luo Shixin was captured by Dou Jiande when the city fell during the Battle of Mingshui, and 'Shixin, with unyielding words and countenance, was put to death.' However, in Chapter 63 of the Romance of the Sui and Tang Dynasties, it is conveyed through the words of Jia Runfu and others that Luo Shixin was 'killed by his schemes' when Wang Shichong rebelled again. The novel not only changed the murderer of Luo Shixin but also altered the location of his death and the background of the battle.