OpenGL is cross-platform, Direct3D is not. Brick rendering is almost certainly custom code implemented directly in OpenGL. That means that to give just the windows users a new feature would require rewriting the entire brick rendering system in Direct3D, and all future updates to it would have to be implemented twice. It would be far more productive to implement regular expressions, because even though almost nobody will use them, it wouldn't ever require maintainence, while implementing Direct3D rendering would require constant updating and bugfixes until it works, and even then it would still need to be updated occasionally.
Of course, this is all based on the assumption that the brick rendering implementation is not generic enough that it would run on Direct3D unmodified...