Maybe I never encountered your perspective; in 20 years in the industry, in about 10 significant software prod/consulting companies, we never outsourced hiring or pre-hiring. From my experience and perception, minor coding tests are a hiring filter than does not gives good results, for both sides of the interview.
You want to hire junior candidates? that test is fun and maybe ok an indicator. Having them live comment/describe/solve existing pieces of code is much more effective and fast. They will still demonstrate ability once on the job, that's what juniors are for.
You want to hire experienced (or even senior) candidates and filter for domain knowledge? 1. Filter on experience & referrals. 2. Conversations: same approach as with the juniors, but much deeper and wider, relevant to your domain. 3. Call at least one reference to counter-check.
A generic fizzbuzz/minesweeper (remember also "code a functional basic blog engine with comments in 30min" back in 2006) coding test demonstrates (in my very subjective and limited opinion) laziness and kind of a lack of interest in the candidate from the hiring person/company.
I understand that when you screen 1000s of people, it gets massive and more basic filters may apply, at least at first contact, though.
> But would you bet on that? Bet your team, your product, your company, your mission, whatever is important to you, on their ability to get things done? I don't think you would. And hiring (and everything else in business) is about making good bets, not about batting 1.000.
I've seen more rejected candidates because of "soft skills" failures than because of technical skills. And much more fired for behaviour than for technical/performance issues. Domain knowledge can be trained, fixed and integrated within the company. Behaviour cannot.