Board Thread:Naruto Discussions/@comment-26403664-20160228225013/@comment-26636534-20160319134105

The regular sword in question was infused with a jutsu, therefore it was infused with chakra, just pointing that out. Also, one possible reason it was able to pierce Naruto's cloak is the same reason that Sasuke didn't use Susanoo to protect himself and Sarada from Shin's attack, plot.

On YM, while being super technical on the databook entry, it says that it reflects any "attack", which is singular and not "attacks" which is plural. So taking that part of the description literally(Which many do nowadays) leads to the notion that the YM cannot defend against multiple natured attacks at the same time.