Board Thread:Questions and Answers/@comment-209.112.218.20-20150405021257/@comment-93.228.142.138-20150611205252

Well Kayaba himself said that he wanted to talk to both of them after the fight and probably set it up that the two of them, whether they die or not will be transported to that crystal platform instead of just disintegrating and getting their brains fired.

If they just died without taking him down he would have talked to them and afterwards would have send the command to kill them, but since both of them overcame the limitations of Kayabas world and in his eyes cleared the game together ( he congratulates both and not just kirito ), he logged them out and send them back as reward. ( well he would have but there was some little disgusting creep that stole Asuna and 299 other players for his sick little experiments so they didn't return to the Real World instantly)