This is fine, except when the candidate knows substantially more than the interviewer about how to solve the problem. I was once asked to implement a spsc circular buffer, and I used C++11 atomics rather than a mutex. I wrote up a working solution, but most of the interviewer's followup questions fundamentally didn't map to my wait-free solution. I spent most of the time explaining to the interviewer how atomics and non-blocking algorithms work. The FAANG rejection email came a few days later.

So I don't think these interviews evaluate the candidate's ability to solve complex and abstract problems. They seem to evaluate the candidate's ability to grind contrived sophomore-level computer science homework. Experience solving the real-life version of the problem rather than the academic one is unwanted.