I was aware of the difference (what you note in your first paragraph), but could not articulate a good explanation of why there is a difference. I found this comment by vi21maobk9vp to be a good explanation, though I feel it could be more clear and concise. I'm not actually sure I could have given you the answer in the grandparent in so few words before reading vi21maobk9vp's comment.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.