Okay, the way I understand the Rasenshuriken is that the additon of wind nature transformation to the Rasengan causes it to achieve a more powerful form with the innate properties of that chakra nature. Once Naruto realises that he needs another shadow clone to apply nature transformation, he manages to add enough wind chakra to the Rasengan that it started to take a shape that reflected that rather than just exploding. But as I said, that was just the equivalent of Naruto's incomplete version of the Rasengan which was barely comparable to the final product.
By the time Naruto joined the fight against Kakuzu, he had been able to add enough nature transformation that it was essentially able to achieve its completed form. Just like Naruto completing the Rasengan and bringing out its true capabilities against Kabuto.
In other words, I believe the act of fully applying wind nature transformation to the Rasengan changes its shape as an innate part of the process (growing four blades of chakra made up of hundreds of miscrospic ones) but not that Naruto is first creating the Wind Release: Rasengan and adding some other type of shape transformation to make it into something more. The task is already so difficult that he splits it between himself and two shadow clones; if he needed to deliberately transform its shape even further then I'd expected him to add another shadow clone to do it. Both databook entries describe it only as "Rasengan + wind nature transformation" which is exactly what Naruto was shown to practice exclusively. The shuriken/blade aspect comes from the wind chakra; every other element used was being added on top of Wind Release: Rasenshuriken which acted as the base template rather than the Rasengan.
By the time Naruto joined the fight against Kakuzu, he had been able to add enough nature transformation that it was essentially able to achieve its completed form. Just like Naruto completing the Rasengan and bringing out its true capabilities against Kabuto.
In other words, I believe the act of fully applying wind nature transformation to the Rasengan changes its shape as an innate part of the process (growing four blades of chakra made up of hundreds of miscrospic ones) but not that Naruto is first creating the Wind Release: Rasengan and adding some other type of shape transformation to make it into something more. The task is already so difficult that he splits it between himself and two shadow clones; if he needed to deliberately transform its shape even further then I'd expected him to add another shadow clone to do it. Both databook entries describe it only as "Rasengan + wind nature transformation" which is exactly what Naruto was shown to practice exclusively. The shuriken/blade aspect comes from the wind chakra; every other element used was being added on top of Wind Release: Rasenshuriken which acted as the base template rather than the Rasengan.