It is sensationalist because it misleads. You see "21 million people with migrant background" and you think of people wearing a niqab who don't speak a word of German. You don't think of people like a Polish psychiatrist or a child whose mother is from Italy but father is from Munich, which make up more than half of this group. Germany uses a very wide definition of the term, which isn't the same as that in common usage.

DW isn't fear mongering on purpose. They probably see that as good news. But even then, it's still misleading. Probably because no one would click on "21 million people have had at least one ancestor not from Germany", because no shit.

And it is 65%. Check the article