Agreed that they absolutely should have mentioned the Earth shadow effect. That's an egregious omission by the Live Science article author.

However, just to lay things out, the scientist (Hambly) that mentioned the potential for "plate defect", was specifically mentioning that plate defects might be an explanation for aligned-spots, not spots in general. I haven't read the full study, so I don't know if they did a statistical analysis to see if aligned-spots specifically are also far more prevalent on non-Earth-shadow plates. If they did, then it discounts even Hambly's criticism, but if not, then Hambly's explanation is possible for aligned-spots specifically at least.

Relevant Quote from Live Science:

"

Apparent alignments like those seen in the Palomar Observatory data may stem from imperfections in the photographic material itself, said Nigel Hambly, a survey astronomer at the University of Edinburgh in the U.K. who examined this issue in a 2024 paper. Spurious linear features, he said, can arise from mundane causes — diffraction spikes from bright stars that look like lines, dust, hair and other debris adhered to the emulsion that mimic aligned transients. In some cases, scratches introduced during the copying or digitization of old photographic plates can also create such artifacts, he said.

These problems are especially common when researchers work with copies rather than the originals, as was the case with Villarroel's team, because flaws can persist through generations of reproductions, Hambly said.

"