But you do realize that they also weed out effective engineers who aren’t good at pointless puzzles, and that leetcode.com and dozens of other sources exist entirely to help people beat this system, right? They don’t measure useful skills. They’re a game that some people are good at beating and others aren’t, and whether that person is an effective engineer is largely unrelated to their skill at that game.

This is exactly right. Puzzles have one solution, programming problems have a solution space. It's like judging an artist by asking them about art.

And it’s (often comically, always depressingly) necessary for this exact reason. In a recent interview my company conducted, the candidate clearly submitted code they had not written as if it were their own. One might be surprised at how well folks can talk, that cannot actually write relatively trivial code.

How did you know they didn't write it?