Top two rows: parts of the final ALMA spectrum centred on the transition frequency of PH₃ 1 − 0 (top left) and five other features, with superimposed the 12th-order polynomials fitted to the local data. Bottom two rows: same with these polynomials removed. We find that now all these features appear at S/Ns above 10 within 60 km s⁻¹ of PH₃. It shows that the procedure followed by GRB20 is incorrect, and results in spurious, high S/N lines.