The Raikage uses his lightning armour and attacks Naruto, but Naruto blocks his attack just in time, I think. This makes B and Tsunade say he's just like a/the yellow flash.
The Raikage says Naruto is the second person to have blocked his fastest punch
And this convinces him the saviour still lives as Naruto
I'd say it says something about Naruto's relfex speed