Comment: Dark degeneracy in DESI DR2 data: Interacting or evolving dark energy?

This record contains the author-prepared preprint of a Comment submitted to Physical Review D on 24 July 2026. The manuscript reexamines the interpretation of the sharply suppressed late-time density-growth curve reported for a geodesic interacting-vacuum model whose background expansion is degenerate with that of a CPL evolving-dark-energy model. It shows that, when cold dark matter exchanges energy, the density-amplitude derivative need not coincide with the velocity-density compression relevant to redshift-space distortions. Direct CLASS calculations find a percent-level IVAC-PPF response over 0 <= z <= 3. The use of the separately conserved baryon velocity changes the result by less than 0.046%, while a 25-point local robustness scan keeps the maximum response below 2.59%. The record includes the manuscript, Supplemental Material, and a replication archive containing the modified CLASS source, patches, parameter files, analysis scripts, validation tools, machine-readable outputs, and checksums required to reproduce the reported results. This is a submitted preprint and has not yet undergone peer review.