the leak is related to texture... not really a directX problem but with directX, texture are cached in the main memory... with opengl, texture are cached in the graphic memory... since graphic memory can be easily flushed, the leak is not really a problem...
In the recent core engine, sins don't leak so much... it will take hours for fill the memory... and if you have a lot of memory, you will not see it...
By the way, almost no big software is free of some memory leak or memory fragmentation...