I've had this happen too. Also, lots of vagueness about what the technical interview entails, whether in terms of tech stack, format (Q&A? Coding exercises? Discussion-based?), or domain of questions (Pure algorithms? Specific applications to role? Both?).

And even when they are specific, it's not very accurate since there's a game of telephone from the person administering the test and the recuriter.

I study hard, I learn new languages and skills, only to get a completely different test. If I'm studying for the LSAT and am handed the MCAT, it's not a realistic indication of performance.