The way I read the Stormwind Fallacy, it's not actually saying anything about optimization or power-gaming at all.
My interpretation is that it's aimed at the false idea that a "weak", "flawed", or "sub-optimal" character is somehow better for RP than one that is mechanically optimal... as if somehow actually being well-suited for the line of work you're pursuing is going to diminish your ability to role-play... when, of course, it's actually quite the opposite.
By that I mean that big, glaring flaws are crutches used by RPers who want nice, easy hooks so they don't have to think too hard about their characters. To make an optimized character "pop," you actually have to dig into the little details to bring them to life.
I've written highly involved characters, complete with detailed personal history, family ties, a Character Questions writeup, 3x3 contact grid, a well-researched cultural identity, and their own set of personal agendas that don't have anything to do with the mission at hand. Characters that I knew, inside and out, like they were a real person.
They also happen to be extremely good at their jobs.
So, yeah, I have to call bullshit any time someone says that playing a "flawed character" is somehow better for RPing.