I think the lie is in thinking FizzBuzz is going to give you any insight into such matters. Put aside your paranoia and just talk to your candidates. Ask them

I think the lie is in thinking FizzBuzz is going to give you any insight into such matters. Put aside your paranoia and just talk to your candidates. Ask them thoughtful questions that invite thoughtful answers. Probe gently to get at more challenging questions. Trust your ability to discern when they're BSing you.