> probably exactly the folks they don’t want to filter out!

Maybe? non-desperate folks might waste the company's time. Usually companies can only give out one offer at a time. If the non-desperate person takes a while to accept, someone else in their pipeline may get an offer and flake.

We had a candidate agree to a start date and then cancel 2 weeks before because they decided to stay at their job.

> “I expect you to intuit what I want and I won’t tell you directly”?

They do tell you directly? "Do this hard uncomfortable task, where the task is study leetcode, completing a coding project."

> Also do they really want to set the tone that “I expect you to intuit what I want and I won’t tell you directly”? Sounds like an awful place to work, right out of the gate.

I have only once had this be a problem and in a way, it was my fault for not noting the ambiguity in the submission. Every other time I have dropped a comment saying "you could have intended A, but also could have intended B so this is when I go back to product and request more information."

That's a perfectly fair and reasonable tone to set because that's how approximately 99% of non-junior jobs work. My boss says he has a problem he'd like me to solve. He might not have all the details so it's on me to investigate the options, identify the gotchas, and clarify the ambiguities.

I never deliberately snuck ambiguities into coding challenges. I've used it in oral sessions for senior and above devs though. "I'm a product manager who wants to add a new feature. I don't really know what's involved but I want you to implement it. Feel free to ask me a million questions and we'll talk it through!"