This is entirely subjective as it comes down to Kent's sense of what needs to be tested, which is arguably a better 'sense' than that of many other programmers.

This is entirely subjective as it comes down to Kent's sense of what needs to be tested, which is arguably a better 'sense' than that of many other programmers. Do you allow your juniors to use their sense? No, you make them hit 100% coverage until they start to learn. As Paul McCartney said: "Learn the rules like a pro, so you can break them like an artist."