If it's something too simple, you're going to be looked down on. If it's a clever hack around someone's bug, it's hard to really be proud of something that shouldn't have had to exist in the first place. If I say something from a long time ago, I may not remember enough details to answer follow-up questions. If my job is boring (hence interviewing for a new one), I may not have had any good "shining moments" recently.
As time goes on, stuff that used to seem or look cool can become embarrassing. I've seriously considered deleting some of the early stuff I have on Github even though it has relatively-a-lot-of-stars for something small and stupid.
Asking to be regaled by stories of tech heroism is also prone to sabotage, because it's easy to rehearse an impressive story. It doesn't necessarily indicate their ability to do things that are useful for the job; it just means they rehearsed a good story and prepared for some follow-ups specifically related to that.
In an interview, you're a lot better off asking questions that will require the respondent to formulate an answer right then and there v. something that they've rehearsed. You're also better off leaving the expectations of tech heroism behind.
"Rock star" job listings have more or less died out, but this is really just a lesser form of it. Typically you don't need or want a rock star. You want someone whose output is professional and consistent.
