[zhte415]

Your post reminds me of three things -

The nature of what's being learnt. Some things require a continuity - to understand B, prior A is needed (or helps, to understand faster).

The method of learning. Book/theory-based, or practical? For either, what's the nature of scaffolding (self, or via resources) to help leap the chasm? If testing one's self, what's the complexity and can that complexity be broken down into simpler (or more discrete) parts, (perhaps testing working better in smaller parts)? Perhaps A isn't fully (or at all) required to 'know' B, depending on how it's learnt. Which goes on to -

The nature of the learner (at that point for that task). Someone that's looking to solve a task, somewhat surface, or someone that's interested and will go deeper into edge cases or approach with greater curiosity?

[I'm skipping the nature of the learning/knowledge, since 'resolving DNS' is a pretty externally verifiable result. However it might be fruitful to consider the nature of the learning is not only 'resolving DNS', and even if 'resolving DNS' fails, learning always happens (intended/unintended, positive/negative, a can of worms there).]

You point out that 'easy' and 'hard' are motivators that might have unexpected, or the reverse, effects vs. intended, depending on the reader. When putting it into those 3 parts, perhaps this shows the usefulness of framing.