Charliehall,
This article wasn’t about what Rabbi Helfgott wrote, but about what Zev Farber wrote. Farber is an apikorus by Rabbi Helfgott’s standard. Farber has clearly decided that the Torah is a broad composite of at least two authors (even if “divinely inspired”). Farber is therefore outside the pale of Orthodoxy even according to Rabbi Helfgott, as you quoted:
“However, the notion of the entirely composite makeup of the Torah has no precedent in classical Jewish sources, and it is therefore impossible to term such a theological understanding as Orthodox in any meaningful sense.”