[glenstein]

>None of that rules out life on other chemistries

Is the upshot of this observation supposed to be that PLATO should change its plans and direct its telescope in a different direction because it has more promising places to look than the habitable zones around stars?

If not, and if you can understand why it's prioritizing that, then why do you take this definition of habitability to be tantamount to denying the possibility of discovering other forms of life? For those possibilities to be relevant to a research program, they need to be motivated by something more than "gee, hey, you never know."

So it's not for lack of reflection on those possibilities that we arrive at this operative definition of habitability. There are pertinent reasons for moving forward with this definition that don't amount to denying other boutique possibilities. Construing it that way I think is just an uncharitable interpretation.