Okon, Sudarsky & Wiedemann's footnote explicitly distinguishes their regress argument from Collins & Popescu's chain-of-preparers rebuttal, preempting the obvious objection
Collins & Popescu (Quantum 9, 1815, 2025) anticipate an infinite-regress worry about their own "preparer" mechanism — their section 5, "Who Prepared the Preparer?" — and answer it by showing that a backward chain of grand-preparers need not be tracked for the conservation balance: "even if there is an entire chain of preparers of preparers, we only need to consider the first." On its face, this looks like it could pre-empt Okon, Sudarsky & Wiedemann's own, separate infinite-regress argument in claim-okon-sudarsky-wiedemann-reference-frame-regress-undermines-preparer-requirement — a reader could object that the regress was already handled.
A direct read of Okon, Sudarsky & Wiedemann's paper shows they raise and dismiss this exact objection themselves, in their own footnote, rather than leaving the overlap for a reader to notice. They distinguish the two regresses: Collins & Popescu's point is about whether a compensating shift propagates backward through a historical chain of preparers — a narrow mathematical claim their own section 5 settles. Okon, Sudarsky & Wiedemann's regress is about something else: whether the enlarged system-plus-preparer composite remains physically meaningful as a pure state without some further frame to define it — a question about ontology and justification that the chain-of-preparers result does not touch.
Source
“Notice that this regress is not blocked by the authors' observation that the grand-preparer does not enter the conservation balance for a measurement on S: the present argument concerns the physical meaningfulness of the enlarged pure state itself, rather than the propagation of the compensating shift.”
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