OK, let me rephrase: It's not much like PPLNS at all. It's more like proportional, only exponentially scored.
The big difference between PPLNS and prop is that PPLNS breaks round boundaries and is not exploitable, and prop maintains round boundaries and is exploitable. Scored proportional is a version of proportional and is exploitable.
That's a very "accurate" explanation and I completely agree with you. I didn't mean to argue about semantics.
I was merely trying to provide a simplified explanation (although not perfectly accurate) which would make it easier to grasp the idea and the differences - especially for people who recently joined the bitcoin mining world.