I have killed people mid-animation and saved them. I have killed other during the animation but after they got the knife kill.
/shrug
Random is random?
I made 2 guys go WTF last night in chat
as I was clicking to det some C4 on their lav a squad mate of theirs knifed me, it let me complete the det even though the knife animation interrupted it, got 3 kills, vehicle destroy/disable and didn't lose my tags