Article one describes the oneness of religion as the claim that earlier revelations and Baha'u'llah's own are chapters of a single unfolding book, with apparent contradictions attributed to human accretion or the lapsing of time-bound law. Structurally, this is not a new kind of religious claim; it is the same fulfilment or supersession pattern several older traditions have already made about their own predecessors, and setting it beside them clarifies what is and is not distinctive about the Baha'i version.
Christianity reads the Hebrew Bible typologically, treating its narratives and laws as anticipations fulfilled and, in the case of ritual law, superseded by Christ, while insisting on continuity of divine authorship throughout. Islam holds that the Quran confirms and corrects the Torah and the Gospel, attributing points of disagreement to human corruption of the earlier texts rather than to error in the original revelation. Both patterns do exactly what article one describes Baha'i teaching doing with all of them in turn: preserve the predecessor's divine origin while relocating its apparent errors to human transmission rather than to God.
What is distinctive about the Baha'i version is its scope and its theory of timing. Rather than superseding one prior revelation, as Christianity relates to Judaism and Islam relates to both, it proposes a single interpretive key applied uniformly to every major tradition at once, and states openly, through progressive revelation, that its own teaching will itself be relativised by a future Messenger, which the Christian and Islamic patterns do not concede about themselves. The structural move is shared; applying it prospectively to one's own revelation, not only retrospectively to everyone else's, is not.