That's not a bug, that's how the scenery have been made. We can discuss its looks, but at least you know it's nothing wrong on your system, nor is really a bug, it's just how is supposed to look like.
The contour is not very rounded, to keep the polygon count down. It's (as usual) a way to simulate what we get in FSX "for free" with the use of details Shaders. Since we don't have shaders in FS9, and the underlying textures were made for FSX *assuming* we would get extra detail over it, we had to replicate that in some way in FS9 using additional polygons.
I'll see if we could at least smooth out that sharp corner, but don't expect to have a fully precise detail contour, like we have in FSX, because that level of precision is not possible in FS9, since in FSX there are no polygons whatsoever, and the application of the detail types is controlled pixel by pixel with the alpha layer of the ground textures.