The book says to "make Apocalypse World feel real". But the example about healing from the book says, "I'll have him erase one segment of harm at the beginning of the next session, and the other one the session after."
Similarly, erasing up to three harm when you're resuscitated (or take a debility) all suggests that harm is an abstract quantity, not a "real thing".
Like any other hit points, why is it that a PC cannot be killed by a bullet? (Even if you take 3- or 4-harm, you can keep going like you're fine.) Harm is an abstract thing, measuring how far you are from death at any given point.
There's fairly little support for the idea that "healing 1-harm" should be considered on real-world terms (whatever that would mean).