You have a point, but it's still pretty tangential at a macro level. The main macro-level thing is that the thread at the top of a page should be responding to the core of the story—or on rare occasions, be something surprising and even more interesting than the story.

The UX of a date picker on the page doesn't clear that bar. That doesn't mean it's unimportant, just that the top of an HN page is not the appropriate context for it. Unless, of course, the story is about the UX of date pickers!