If you think Mortis conclusively proved Anakin is the Chosen One you are gravely mistaken. We know he is from interviews with George, but Mortis does nothing to confirm or deny the accuracy of the prophecy itself or Anakin as its implementer. All we find out is one guy's interpretation of it, that's it. And, on top of that, we do find out conclusively that that one interpretation the arc was based on was false (since obviously Anakin didn't stay on Mortis). It seems to me that the belief that this arc conclusively proved anything about the Chosen One prophecy may be merely the result of people who need an excuse to whine because they refused to put enough thought into the arc to gain anything from it. Your second point is exactly right, which is why your first is irrelevant.