>The implication seems to be that students can't do the trial-and-error, understand then apply the theory. I agree with parent comment that this is awfully defeatist.

All teaching is a balance between various factors, and perhaps the instructor didn't get right in this specific instance.

Ideally the instructor would teach the theory, allow some trial-and-error as students grapple with new information, and then step in with prodding towards how to do it - but fundamentally, there is a limit on how the instructor can let the class wander without needing to move on to cover the rest of the material (this wasn't a special topics class covering how to solve this one specific problem).

Hence, go through the information but provide the technique involved after suitable time passes. That's just the nature of teaching/learning when the students don't have infinite time to essentially re-invent the material they are trying to learn.