Yeah it does seem like he's sending a message to his own children just like Kishi was doing for us.It's possible that Kishi is sending a message to his own children. However, still, it doesn't make sense
for Naruto nor any body else to realize he can duplicate himself pretty easily and handle multiple things
at once. And when his chakra levels, splitting into two or three for a whole day is no issue whatsoever either.
I don't know, It seems like maybe Naruto lost all of his chakra possibly to build that city? xD. We'll have to see in the movie