Actually... it is how the real world works. Every product you touch, use, consume, etc... all has several design elements whose sole purpose is to avoid a similar situation and protect you from yourself. I've been in software QA for a long long time and in near every situation where the developer is saying "I'm not going to change it, the user shouldn't do that" and the QA says "Doesn't matter, we can address it so it can't happen", the QA argument wins. And in the few instances where they didn't win, it was usually because it was caught too late in the cycle, in which the issue gets addressed post-release. In instances where the product breaks, it gets addressed, every time.
Now, sometimes these potential problems should have been caught before release.. which I think the S-Pen issue most certainly should have. I can only guess that that switch was the result of a design change late in the development cycle and not properly tested... or they discovered it too late to change it. That happens more than people think. But other issues, well, they just can't be caught.
A perfect example of this, albeit a much more extreme example, is the huge ignition recall that GM had to do back in 2014... the one where the ignition mechanism was getting worn out by people who had everything but the kitchen sink on their keychains. GM caught a lot of flak for that, but from a testing standpoint, who would have thought to ask that question during the R&D phase? Now, the simple answer would be "Stop doing that!", but 6 people died as a result of the airbags not going off due to the ignition failure. GM recalled 1.6 million+ cars.