There are more reasons than that to perform good, I guess that's what the classic "where do you see yourself in 5 years" is trying to judge. But in general this is a problem, yes.

More importantly, the fact that FizzBuzz is used to the point of being a cliche is already admitting that given just a CV and a verbal interview we are unable to reliable judge if a person can even program at all.

I like how it's always that the hire is to blame for their skill level in the organization once they are hired. How come we don't ask whether companies know how to hire? Like, publicizing firing rates, turnover, that kind of thing.

I mean, I know why, but it's never a part of the rubric. "We stopped using talk interviews and our retention went way up. We used to see 1/3 of our hires quit within two months of their first salary review." This is probably a more reliable approach the more a company promotes from within, and my sense is that many-if-not-most startups do not.