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.