I've done this at a few companies as a hiring manager--offer the candidates a 10 hour/week (or whatever they can commit to) contract to do X thing until Y date. They set their own hours, but they can't expect folks to be available afterhours. Evaluate how far they got based on the hours they committed. Typically shows how their work style will be, but can't really evaluate their interpersonal skills/"meeting persona".

Sounds great for entry-level, and terrible for people leaving jobs for new ones. It's an enormous life-changing decision to invest energy into leaving a job for a new one. I'm never going to do that for "a 10 hour/week contract to do X thing until Y date", and neither are any of the people I'd love to hire.

So how does that work if you are in another job? Most contracts forbid working for another company. And if they aren't in another job how do they pay bills on ten hours a week?

The contract to hire contracts I've worked as a developer the past 30 years were either 3 month or 6 month periods and 40 hours per week.

No offense but I'd be highly suspicious of someone offering contract to hire only 10 hours per week, it doesn't sound like the company has much skin in the game.

I think you're replying to a post proposing 10/week instead of the 30 interviews. Not instead of actual hiring.

Would work just fine for both parties if you're employed and open to changing jobs, for example.

10 hours/week is really just a compensated job interview.