Strictly speaking the "Stormwind Fallacy" deals with the idea that optimising and roleplaying are
not necessarily mutually exclusive: entailing that they will in fact be mutually exclusive
sometimes. (That can be demonstrated by working through some subsets and their intersections, or lack thereof.) SF really just resists jumping to conclusions on that score.
I suspect that this line of argumentation amounts to a red-herring. If I have an RP concept that doesn't fit that stat array then "Yes" if I am forced to take it I am very likely to be jolted out of the story. On the other hand, if I have an RP concept that does fit that stat array then all may be well. Logically, we can consider the set of all possible 5ed characters. By definition, not all of those characters are optimised. And for a given player, not all of those characters may be RP-able. Thus for some player, there may be found some subset of OP characters that are not RP-able.
Wanting to optimise i.e. minimax can sometimes interfere with wanting to roleplay. The important point of the Stormwind Fallacy is that it doesn't
necessarily do so. A given player may be able to meld their RP and OP due to their specific choices on each axis, but for another player there may be RP-able characters that are not OP-able. I think where RPers and OPers often run into misunderstanding is on which they prioritise: whether they bend their fiction to fit their stats, or their stats to fit their fiction. For an RPer, doing the former jolts them out of suspension of disbelief so they find it difficult to endorse. Both camps can make the mistake of dissing the thing the other enjoys.
This is well-worn ground. When I first read the OP and his "Tempest" cleric, I thought he was trolling (Tempest Stormwind, geddit!) If so, that's fine with me. It's an interesting subject