I think this article gives a bit more background.
Obviously now that there are soon upcoming new telescopes sensitive enough to do direct planetary observation of their reflected light spectrum, people are going to look for unusual spikes.
This is similar to the paper recently released about the potential biomarker found in the same way on Venus.
I think the researchers are mainly saying that people should look at these spectral analysis with an open mind and not dismiss “Aliens” out right as a possible explanation (in their published texts).
Pollution is now the the main criteria for intelligent life
Even that is a bit iffy, because if aliens are sufficient intelligent and efficient then it possible that there are minimal to no pollution.
As long as there is no better idea on how we might identify potential candidate planets based on observation with telescopes only, I don’t see how this would be relevant. Sure there might be false negatives.
