I've had some experience with flaky colleagues asking "why" without putting much effort into understanding what was actually said. A more specific question addressing the person's lack of understanding in some area reflects sincerity in wanting to know rather than just wasting other's time with "academic" interests. You'll be surprised by the number of times when why is asked in return, the answer is disingenuously "just curious."

Your two questions could elicit a better response, even though it's basically the same as "why," because it's at least showing a semblance of effort and the interest to probe deeper.