Do you think the current Magneto was a construct Wanda created in order to make the loving dad she always wanted and never had? The one who pretended to be Xorn was the original Magneto who remained a tyrant, but went over-the-top crazy from the kick drug. It would appear the post-Magneto was much more caring and not as extreme as he was before. All of that sounds like a more logical explanation to the ridiculous Xorn twin brother retcon.