Thought of the same theory as you. HOWEVER
It is based on whoever kills the king first, which is how it applies to this. IE in checkmate, the losing colour can still move another piece, but the winning colour simply, "Kills," the king.
What is this "kills" the k. It's a game that ends at checkmate... not some silly arguement who or what king is killed first.Grow up, and concertrate on your homework.
The OP will like this one:
http://www.chess.com/forum/view/daily-puzzles/1242013---mate-in-5