I think that they *have* "missed" something.
Nowhere in my post did I say that it was necessarily a design flaw. I would have thought however, that a company as famously "particular" as Apple would have ensured that there was some form of random "batch-checking" of manufactured phones (independent of their "fabber") that gave them a reasonably reliable picture (statistically speaking) of what they could expect, such that they were working on a fix from the get-go? It does indeed surprise me that this appears to have caught Apple on the hop. They have after all built their reputation on the quality of their hardware, have they not? That some duff parts may have got into the supply-chain may very well be the explanation (or at least part of the explanation) for this. That however does not explain why this appears to have come as a big surprise to Apple.