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”

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.

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.