This is different though: the bug is so bad that random, inexpert users can discover it by accident. People that are not going to even be familiar with the term

This is different though: the bug is so bad that random, inexpert users can discover it by accident. People that are not going to even be familiar with the term "responsible disclosure" at all. This may have been the case for the guy who tweeted this. There is no realistic way to keep a lid on something like that and so in this case the blame is entirely on Apple.