I don't think this matters. If he strongly claims he is an expert on Flask, and I knew Flask, then I would test the depth of that knowledge. You can't validate

I don't think this matters. If he strongly claims he is an expert on Flask, and I knew Flask, then I would test the depth of that knowledge. You can't validate every detail on their resume, but if you find they misled about this one fact, odds are they mislead on other facts you are not capable of validating.