I doubt you'll receive a fix since this isn't technically a "bug"; it's a firmware configuration choice that Dell made, and they made it on some other systems that have not been "fixed" either.  Starting with the 9370 model, the XPS 13 now allows full speed operation, but again I would not expect that to be back ported to older models even though obviously it would be nice.

Dell hide this information when they are selling XPS 9360 .  if I know this point I would change to other brand. MI notebook was also limit the speed at the beginning, but they can fix it by update bios.