I think a critical part of his point is that what you build and what you model are neccessarily two different things. You can totally simulate it, and then when the rocket inevitably fails, you can go "aha! This bit deviated from the simulation!" But you can't feed that forward beforehand to prevent the failure, since you can't
expect random acts of poor workmanship or crafting. You can only prepare and hope (and you can do that with shockingly high confidence - but rockets are more than equally shockingly complex.)
Part of what makes the idea of bringing the first stage back to the pad so important is that we so rarely get to use the same engines multiple times in the field (where all the really nasty reality checks are done). Being able to reuse stages allows us to far better model how they will perform in the future. Otherwise, we're using test beds to feed parameters into sims to inform our launches; it's good practice, but more physical evidence is always better.
