Except the fix doesn't actually fix this, since it's still the case (unless this changes when we come back from Secret Wars) that everybody thought they were Magneto's kids for years and the timeline made enough sense that nobody questioned it on that basis. So, the twins still need to be just as old (chronologically speaking, with the suspended animation or whatever) as ever, or everybody would have been counting on their fingers and going, "Uh, but hey, guys, aren't you too young for the cow woman's story to make sense?". Changing their actual origin doesn't change that.