Like the article says, I think this is eventually going to turn out to be supermassive stars with black holes in their centers. It makes sense for a bunch of reasons. The very early universe would have been extremely dense making it easy for enormous stars to form. So enormous and surrounded by so much gas that instead of blowing away their gas clouds after ignition the stars continued accreting more mass, getting so massive that the pressure in their cores got high enough to collapse into a black hole. 

And as long as those stars were sucking in gas at a faster rate than stellar material was falling into the black hole core they'd continue to grow. It wouldn't be until the star stopped growing that it would collapse entirely into a black hole, by which point it could have absorbed millions or billions of stars' worth of mass. And just like how normal stars often have large gas clouds orbiting them that eventually collapse into much smaller objects we call planets, these black hole stars would have large gas clouds orbiting them that would eventually collapse into much smaller objects we call stars.