Is it 25% will do it properly, 75% don't? Am I too cynical about tech interviews, or too optimistic?
I'd also add, for a couple of companies, Google's approach springs to mind.
I think for places where, you know, they do search algorithms, knowing how to print the spanning tree of a graph is probably an important thing to know.
Personally I think there's a strong correlation between necessity and hiring quality (i.e. if teams really need the help, they typically engage candidates more meaningfully than the Google-style clinically impartial methodology)
Sounds a bit like what my old timer buddy says.
Google's KPI is hiring talent away from competitors who physically live in the San Francisco bay area. And the ads/ML teams that they drench in their 1%ers.
Everyone else is window dressing.
From a cultural side, some companies have a competency pillar that is supposed to embody the idea of being a "good person". In mine, we call it "Citizenship", it's tied to performance appraisal and interviewing is one way to develop that competency.
As for code cleanliness, I've passed candidates with messy or even broken code before, if the candidate demonstrated competence in enough other aspects and the code quality issues can be attributed to nervousness or running out of time half way through a refactor or whatever.