Board Thread:Theories and Speculation/@comment-31119074-20170122152801/@comment-734582-20170128180401

Lorenzo VonMT wrote: Nah man, that doesn't justify it. This is a task the 4th hokage who was a genius among geniuses couldn't complete because he died early Except Boruto didn't create a full-on Wind Style Rasengan.

We've seen the steps to Rasengan: concentrate chakra, add rotation, add power. Wind Style adds a fourth: Nature transform.

It seems that Boruto switched the final two, and thus created an under-powered rasengan. We don't really know if the Rasengan at the end of the movie is a Wind Style or a regular one.

Secondly, judging by the Fifth and Seventh, the hokage position is actually a really busy position. I doubt Minato ever got around to properly adding his release once he became Hokage. Unlike Naruto who put in several years worth of continuous training, Minato was also busy with a war. The actual training time he put in is thus much less.