The Short Version
The pharaoh's ritual role in maintaining Ma'at to sustain cosmic and social order is well-established across authoritative Egyptological sources, including the Fitzwilliam Museum and peer-reviewed scholarship. The claim accurately reflects the standard scholarly consensus that the pharaoh bore a uniquely official and primary ritual duty in this regard. Minor caveats apply: ordinary Egyptians and priests also contributed to upholding Ma'at, and the "required" framing reflects theological ideology rather than a proven causal mechanism.