"The Dark Lord came to Godric's Hollow," said McGonagall in a whisper. "You should have been hidden, but you were betrayed. The Dark Lord killed James, and he killed Lily, and he came in the end to you, to your crib. He cast the Killing Curse at you. And that was where it ended. The Killing Curse is formed of pure hate, and strikes directly at the soul, severing it from the body. It cannot be blocked. The only defense is not to be there. But you survived. You are the only person ever to survive. The Killing Curse reflected and rebounded and struck the Dark Lord, leaving only the burnt hulk of his body and a scar on your forehead. That was the end of the terror, and we were free. That, Harry Potter, is why people want to see the scar on your forehead, and why they want to shake your hand."

Saying that a spell severs the soul from the body comes along with the strong implication of not killing someone via bodily harm.

He hasn't heard the incantation yet, that's true. But he just heard plenty about the Killing Curse.

edit: I'm fairly confident that the concept of magic forensics is not beyond him at the moment.

Besides, looking at it narratively, there has been way too long of a wait to find out what that meant for the payoff to be minor.