That's not a typical leetcode problem though. Most companies ask things like "solve this slightly modified knapsack problem" which takes 5 minutes if you know the solution and 50 minutes if you don't.

Yeah, it's very intentionally not a typical leetcode problem, precisely because leetcode is nearly worthless for screening people these days. I was replying to someone who seemed to be objecting to my opinion of some candidates' skills on the basis that maybe they just didn't know the specific thing we ask.