[freehorse]

But why ask about "the hardest day in your life" instead eg "the hardest day at work"?

Personally asking this kind of personal questions sounds very weird. You can evaluate soft skills and culture fit by asking more relevant, professional questions. Except if the reason to ask this kind of more personal questions was sth else.

[cwnyth]

Notice that the blog post author did not provide exact quotes. In fact, they explicitly state they do not remember the wording. It's very likely that they did, in fact, ask about biggest challenges, and the author misunderstood.

[TylerE]

The cynic in me says because they want to select candidates whose work IS their life.