rasenshuriken cannot be "that jutsu".when jiraya told naruto not to use it,naruto didnot know rasenshuriken he learnt it afterwords...He might be or he might, but a few things are for certain the jutsu we see him working on is not the Rasenshriken cause the Rasenshriken makes a huge creator and the image we see is of a slice. So this could be what he is taking about because Sage mode gives him a large amount of power to perform this jutsu without going into fox mode(and naruto wants to save everyone with his own power, so thats why he doesn;t like fox mode that much now)