True, that spot isn't where you would get a crack from a drop, but it does look like the type of thing that might happen if you were trying to pry a case open. No one ever said anything about a drop having to be the cause of the crack.
I have to agree with mick4394 concerning the missing piece from the right palm rest of this MacBook. I've looked at the provided picture over and over again three points keep sticking in my head:
1. It looks like a really clean break on a surface where the pressure required to open the MacBook lid is spread across an area that does completely match the missing piece.
2. The pressure required to open the MacBook lid (at least mine) can't be more than ~5lbs per square inch across the front surface of the case, which is not nearly enough to shear a piece of any size from the palm rest as displayed in the photo. Perhaps if there was already a crack in that area, but not by itself. I've heard of screws on the MacBook causing case cracks, but I do not see any screws under the palm rest in this area.
3. I reviewed a lot of MacBook case crack pictures when I was researching my MacBook before purchasing, but I've never saw one with damage like this.
http://img.photobucket.com/albums/v512/Flickie/crack2.png
Given these reasons, I too can understand why Apple might question fixing this particular damage under warranty.