This article isn't about a search for technological civilizations. Its about spectographic analysis of exoplanets, which can be used to detect organic molecules in the atmosphere.
You don't really need to detect organic molecules. If anyone detected 21% oxygen (O2, inorganic) in Earth's atmosphere, they sure knew something was going on. Lifeless planets like Venus, Mars, have atmospheres that are close to chemical equilibrium. And Earth's atmosphere is far from equilibrium, free oxygen it much too reactive and wouldn't exist without photosynthesis continuously producing it.
Our understanding of astrochemestry is still limited enough, that we cannot say with confidence that a given signature requires a biotic process to produce.
It will always be possible to find a new extreme edge case to deny far easier and more common processes that leave around biosignatures, it's the exact same rhetoric used to handwave away the methane in the martian atmosphere.
They have a new preprint that argues that Assembly theory can explain and quantify selection and evolution in complex systems: https://arxiv.org/abs/2206.02279 (I think that it is one of the more under-appreciated papers out there).