

Yeah, the issue is not “Microsoft’s usage of the XML format”. The issue is that they blatantly bought their format’s standardization, and then intentionally released an implementation that substantially deviated from the specs, making sure that MSO was the only “compatible” implementation.
Try it, you might be surprised. I played WoW under Linux like 15 years ago, and for a couple of patches WoW ran much better under Linux than Windows because of a bug in the GPU driver or something. The Wine folks handle buggy Windows software all the time, and might fix bugs that MS won’t bother with.