Board Thread:Boruto: Naruto the Movie/@comment-27828147-20160219143650/@comment-734582-20160606104844

ThrowingHands wrote: Vanishing rasengan is less effective than an actual rasengan, in my opinion, It's essentially a mini-rasengan that fails. The surprise part is simply that the energy in the attack is carried a greater distance than one would expect.

this is why Sasuke brought Boruto. If Momoshiki can be tricked into believing the technique simply failed, he wouldn't bother to absorb it.