This is not a gaffe.
It was published 8 years ago. You cannot expect anyone as computer and internet savvy as the Obama campaign to “overlook” these facts.
They just didn’t think they would be called out on it.
You are correct, in the real sense of the word it is not a gaffe. But, I think the Obama people have enough sense not to make fun of a war hero’s injuries. What it points out is their desperation and stupidity. They are like dumb kids who act before they think. It’s also an indication of the kind of president Obama would be.
That ads some irony to this whole thing since it is criticism of McCain’s lack of computer use.