I think they're answering different questions. Your scenario 1 gives good reason to think that using probabilities is a good way to handle at least some types of logical uncertainty. My question was about empirical or indexical uncertainty. For example, why do we think one kind of universe is more likely to exist than another, or why do we think we're more likely to be in one kind of universe than another (depending on whether you accept the idea that all possible universes exist)?