I'm surprised that no one has suggested the obvious: Yes, tech interviews are flawed in the literal sense: they don't measure genuine or practical programming ability.

However, it's illegal for companies to require IQ tests to screen employee hiring, and these sorts of interviews seem like a pretty clear stand-in for an IQ test. It's doesn't really measure your ability to be a programmer, but act as a good-enough replacement for an IQ test: The problems are hard and complex, and require that someone does actually spend the time to learn the problems.