I agree with your analysis. But gwern's description of Harry's victory over Voldemort as a "black swan" doesn't satisfy me. The canon explanation - that the Power of Love auto-defeats all dark magic, and either no one had ever noticed this before, or Voldemort just assumed no one would use that strategy despite its obvious game-winning power because Evil Cannot Comprehend Good - doesn't seem like the kind of thing that would cut it in Methods. One remote possibility is that Voldemort realized he'd inspired so much hatred that he'd never be able to unite the magical world without first breaking its power so badly it would be useless to him, so he found a kid with Dark Lord potential, stuck enough of his soul into him that he felt in control, and then faked his own death in such a way as to make his chosen heir the sort of hero whom everyone would rally around. This is probably too complicated for a smart Slytherin who'd seen The Tragedy of Light to try, but there's got to be some sort of weird explanation for why Voldemort lost ten years ago, and why he lost to a kid with precisely the sort of plotting ability and mastery of Muggle methodology Voldy needs for his plots.

I can't reconcile that theory with the combined Voldemort-Quirrel history. (I did think of it after the discussion about scientists nearly dooming humanity.) I don't think it works. Quirrelmort snuck into NASA in the '70s, when the Voyagers launched. That is, decades before his defeat. Quirrelmort knew of Voyager, knew where to find it, knew what building, what campus, how to defeat the many security systems, and so on. This bespeaks an intimate and long-standing interest in NASA's projects. Given the horcrux is a large fraction of his life, it also means Quirrelmort trusts rockets a great deal. Which means he trusts in The Power of Science. Nukes, nuclear winter, and other existential risks were definitely common knowledge in the '70s. Quirrelmort couldn't've possibly missed them, especially with things like Project Orion. So, he knows muggles can kill all humanity and also wizards; he believes they might do it; and yet, it's only after the Black Swan of Harry that Quirrelmort suddenly realigns all his priorities? Well, I'm sure a good author could write that and make me believe it. But I'm not going to make myself believe just to explain away Quirrel's speech.