“Signs of life” has more information content than “Phosphine” - I had no idea that Phosphine is a sign of life, and that is a completely objective description of it from my new understanding. A sign of life does not mean life.
My understanding is that the presence of it strongly implies life on Venus. Just because people have a prior on that doesn't mean the evidence is inherently weak. If it turns out there is bacterial life on Mars and on Venus (both potentially the case) people who claimed we needed "extraordinary evidence for extraordinary claims" will look conservative in retrospect.
