The specific wording was "most Christian churches", which given how many different denominations there are in protestantism is probably accurate, although I do not have a source for this.

The GP’s comment sought to marginalize & disrespect a religious text by misrepresenting the text's prominence within its own religion.

I suspect we would not be playing word games, if they instead said that SuperNotes is not a real notetaking app and justified it with “notetaking means a lot of things to a lot of people”

The work to marginalize/sideline those texts was already done by many others over an extended period of time, GP was just pointing that out (and pointing out why they have done so).

I would be happy for you to say that Supernotes is not a note-taking app if instead you felt it was more of a knowledge-management app or a digital zettelkasten system. Note-taking does mean different things to different people. Some people don't think it's effective note-taking if you're not doing it with pen and paper.

yes. the weighted (by membership) majority of denominations clearly includes the full canon with what the minority labels "apocryphal" scriptures.

The original statement went for "most Christian churches", not "most Christians" (what you'd get with your "weighting"). Maybe a useless metric but the one chosen up-thread.

Going from there to implicitly weighting by membership seems rather arbitrary: I could also claim to weigh by readership (or hours of reading, or any other metric that includes actually working with the text) which might give a pretty different result, given how the idea of individually reading and interpreting the Bible is a major raison d'être of Protestantism.

there are hundreds of denominations and thousands of "independent" churches. we can argue in which way we weigh their voices, but not ignore their sizes completely.

A perfectly good case to make (I'm not quite convinced by "most churches" as a metric), but doing so is different from moving goalposts and calling it "weighting".