I'm not Shana, but I think I know what she means. I'm not sure how to explain it clearly but I will try.
Fact: The bigger the bust, the more space it takes up. Therefore, a big bust makes the torso appear shorter. If you are already short-waisted like Shana and I, you don't have a whole lot of space left that isn't consumed by your bust! I have very little space between my bust and the top of my hip. A longer shirt breaks the body's proportions up differently, so it looks like there is more breathing space between the bust and hips.
I'm grabbing this image from Imogen as a visual:
http://www.polyvore.com/golden_mean/set?.mid=embed&id=9825963
That said, I like shorter tops with skirts as well and manage to wear them despite my short waist/big bust. I think defining the waist, however much or little there is, is key, which is why this outfit worked;
http://img.photobucket.com/alb.....G_2230.jpg
But also why long shirts work just fine when belted, or with some sort of band across the waist. The latter has been my trick in finding skirt tops even though I am generally way too short-waisted for them to fit off the rack.
(AJ I am short-waisted and have a long rise. It is definitely possible and surprisingly common)