I think your (b) is what's most relevant here.

That is, I generally interpret the recurring "what if your thought leader is wrong?" threads that pop up here as an expression of the expectation that reasoning cannot be judged (either in the specific context, or more generally) except through evaluation of the results it endorses after they become actual.

There are varying interpretations I make of that expectation, depending on specifics and on how charitable I'm feeling.

Some of those interpretations I even agree with... for example, I would agree that it's much easier for me to fool myself into inaccurately thinking a line of reasoning either makes sense or doesn't make sense, than it is for me to fool myself into inaccurately thinking that a specific prediction either happened or didn't happen. (Both are possible, and I've likely done both in my time, but the latter is more difficult.)