It's not whether you can solve it right away, it's how you approach the problem solving process to reach a viable solution. If "try to prove that this code is actually correct" is part of that process, that's the kind of "trivia" that can really be widely applicable even in a working environment, in a way that random leetcode algos often aren't.

I vote for making "how would you think about proving this correct?" a question in all algo-focused interviews.