I forgot I came across that before a while ago. I did a bunch of testing following up my previous post and it's because of how the game engine draws textures. The game draws them internally as 2 triangles positioned top-left and bottom-right. Each triangle uses 3 points from the texcoords to render the image.
I'll just bring this image back from the other post...
In this example, the bottom 2 texcoord points were widened past the bounds of the image. The bottom-right triangle stretched properly while the top-left one merely skewed the image. I'm assuming if the top points were widened instead, the situation would be reversed.