Article one's caution, that no medieval source lists all nine worlds and that the tidy modern scheme is a reconstruction, describes the state of the philology. It does not describe the state of contemporary practice, where the nine worlds now function as settled cosmology for a living religious movement rather than as an open scholarly question.
Modern Heathenry, the revival and reconstruction of pre-Christian Germanic and Norse religion, has organised bodies with legal recognition: Iceland's Asatruarfelagid was registered as a religious organisation in 1972, and comparable groups exist in Scandinavia, North America and elsewhere under names including The Troth and the Asatru Folk Assembly. For ritual and devotional purposes, these communities generally work from the nine-world scheme in its assembled, textbook form, treating it as the cosmology of the tradition they are reviving rather than foregrounding the manuscript disagreements article one describes.
That is not error on the practitioners' part so much as a difference in what each account is for. A philologist reading Voluspa and the Prose Edda side by side is bound to report where Snorri's thirteenth-century systematising outruns the older poetry's evidence. A religious community reconstructing practice needs a cosmology to build ritual and teaching around, and has generally adopted the same nineteenth- and twentieth-century synthesis that academic Old Norse scholarship treats with far greater reserve. Both positions can be accurately described without either one being wrong about what it is doing.