I think the idea is you have many cherished ideas, and so many are actually false that you shouldn't have much difficulty killing one.
Or, another way of looking at it, your knowledge of so many areas is superficial and a deep dive into any one would let you know how you weren't even wrong, as the saying goes.
You can find people doing it in any HN thread about almost anything - often shows up as "why didn't they just do X". A non-domain expert with a "obvious solution" is almost always missing something major.
A better way to phrase it would be a year when you don't challenge your idea is probably a failed year. It might still win the challenge.