If you're going to expect the person with the answers to take the mental effort to figure out what the questioner does and does not understand, then I think it's also reasonable to expect the questioner to be honest and say "I don't understand what you just said" when it's true.

You claim it's obvious what the questioner does not know. I claim it's not. This is why teaching is hard. Having the answers is not enough. The hard part is sussing out what the student's incomplete or incorrect understanding is, then guiding them to something more complete and correct. This takes time, patience, and a surprising amount of effort on the part of the teacher. If you don't believe me, then try teaching people with zero programming experience how to program.

When it's someone's job to do that, well, that's their job. Students are often reluctant to say "I don't know what you just said." I had to read their faces to gauge understanding, or I'd have to ask them to repeat back to me, in their own words, what I just explained.

But we're talking about peers. And if peers are going to learn from each other, then there should be an understanding that teaching is hard, and that the person asking the questions has just as much (if not more) of a duty to be honest.