Bullet time or not it's probably just a liberty the animation took so that it would look cooler, I highly doubt that the LN goes "And so Kirito stabbed *grunts name* while *grunt* screamed for 20 seconds and then perished". Seriously no one would ever write something like that other than perhaps that it felt like it took a long time to kill him.
As I mentioned with the convertion system we don't really know a lot about it so it could be that he simply got to keep the name he had in ALO by default or he picked it himself. Besides other than the people in SAO it doesn't seem his name is that well known since they kept most things under wrap otherwise they'd have arrested those in that PK guild.
Sinon wants to kill Kirito and she makes it as clear as she can. I don't think she expects him to make it there but she wants to kill him and still pissed off so what else is there to say?