Speed!

[General Naruto]

You do Know Body Flicker is just using Chakra to hasten your movement in a smack explosion of speed right?

 

[Howling Fox]

Naruto Shunshin is so fast he is invisible you only see a flash like minato w/ FTG Hokage Naruto would be flash speed in shunsin especially w/ Rsm cloak up

 

[Michael]

Naruto Shunshin is so fast he is invisible you only see a flash like minato w/ FTG Hokage Naruto would be flash speed in shunsin especially w/ Rsm cloak up

Exactly, its funny how these people believe that was shunshin in the boruto movie. XD

 

[Dark Sonic]

Shunshin is, in the end, just high-speed movement. It appears instantaneous in short distances, but that's not the case when there's greater lengths to be crossed when the speed can be more easily perceived. Remember BM Naruto leaving a trail? It could be argued this was the same.

Although, I myself don't believe they used Body Flicker at the initial charge. I think that was their raw footspeed, and then Sasuke used a Shunshin to up his speed and attack first, though that's iffy as well. It's not known for sure what that speed was, my belief is that they they didn't use Shunshin.

This right here. I didn't watch the movie but I saw the scene where Naruto and Sasuke started running. Running → Shunshin.