If you see the anime, his sword was phasing through yamato's kunai without cutting it, although I doubt it was shown in the manga.
Nah he used lightning to enhance the blade's piercing ability
Or you know there is different kusanagi blades. Why would Sasuke name a blade Orochimaru gave him out of respect when he didn't even respect Orochimaru? Kusanagi and totsuka are cut from the same cloth yet have totally different mechanics and abilities. Same as these.
I don't think there were different ones because Orochimaru always talked about it like it was unique and emphasized on its ability to stretch. When he faced Itachi he also said Totsuka was the opposite/counter of Kusanagi, not Kusanagis.
If you think about his statement, the ability to stretch counters Totsuka's ability to absorb. He was referring to his blade implying his blade is Kusanagi not Sasuke's.
I'm sticking to the idea Sasuke gave his katana the same name because he managed to make his blade pierce through anything like the original Kusanagi was capable of doing, the difference is he uses lightning to do so.
It's not out of Sasuke's nature to do something like that because he's known to acknowledge other people's power by adopting their feats in some way. Naming his blade Kusanagi could be a nod to Orochimaru's influence on his sword skills.