That's not it though.
Pretend I was hiring a restaurant chef and the industry standard test was "run a mile in 4 minutes", a test that 98% of all candidates fail!
So professional chefs practice by jogging daily so they could prove themselves during the famous "run a 4 minute mile" weeding test so they can be hired to prepare meals for people.
That's what we're talking about here. I've had to write out the mathematical proof of various algo complexities of B* trees exactly 0 times when writing SDKs for some CRUD application but that's what's expected during the interview.
It's as correlated with the ability to do the job about as much as running a 4 minute mile in that younger, more desperate, easier to control, and thus cheaper people can do it better. That's what the actual filter is for - to find candidates that are easier to abuse and take advantage of - smart enough to do the work and foolish enough to take the job.
I've hired large teams at multiple companies where such tests were used and that was exactly why we did it. We didn't want the experienced 45 year old wanting to work 40 hours with vacation, we wanted the foolish 25 year old that gave us their weekend.
Actually saying that is illegal, but using a stupid test that selects for it is not.
