I understand that some people are concerned that they're competing with candidates who will put in 12 hours to do what they should be doing in 4. But that's not their problem. Their problem as a professional is to evaluate whether they can do the challenge in 4 hours; that's the expectation the job is setting.

It is perfectly reasonable for someone to look at the hiring process we're running and say "no, this communicates to me that this job wouldn't be a good fit for me". That's a good outcome! Most jobs aren't a good fit for most people; that's the whole challenge of hiring.