Right that's true, it does come down to the manager's level of expertise. I guess my point is that you need someone with a solid understanding of code to review

Right that's true, it does come down to the manager's level of expertise. I guess my point is that you need someone with a solid understanding of code to review their output, not just a manager evaluating "does it work", whether that reviewer is another senior engineer, the CTO, the technical co-founder, etc.