The two aren't mutually exclusive. He might be getting his head on the ball but if the quality of contact is crap then it doesn't help much.
One of our biggest defensive problems this year is giving up second phase possession after set pieces. We often get to the ball first but we can't control and clear it properly, giving the opposition quality second chances to score.
That's not just on Ibu of course, but you can see with your own eyes his technique ain't great.