As the friendly article explains, it is next to impossible to differentiate between "fake job interview" and "unsuccessful real interview".

In the absence of proper documentation and genuine feedback, assume it was a fake.

E.g. I had a CodeSignal assessment recently that resulted in the end of my "consideration". If it had been a genuine opening, they'd be able to tell me what the expected score was and how tenured peers at the company are scoring in recent assessments.

Most companies refuse to provide applicants any feedback other than yes/no, because it opens them up to lawsuits.

Really? Guess they'd better make sure they aren't discriminating unfairly, conducting fake interviews, or doing other things that would get them nailed by a system that exists for good reason.

Evidence that a test is a proxy for IQ means you’re gonna lose in court.

No it doesn't. IQ tests, even explicit ones, are broadly legal in the US.

bait & switch jobs should also be fraud

Make it a criminal felony for everyone involved with fake job posts. It's wage theft of people who aren't even the company's employees. In almost all other contexts this would be criminal theft. Make it criminal theft in this context too. Once you include the hundreds or thousands of people they've stolen labor from, it easily passes any threshold required for it to be a felony.

Guarantee the ghost job nonsense will instantly stop once the first person is shown being shipped off to prison for a year and one day.

This might move hiring to friends / network type hiring. If you were in a good network awesome. If not could be tough