You're right, Cujo also shouldn't have validated. In a previous version of the post `neutered` was nullable and `age` was optional, but I decided to save the discussion of nullables/optional until later so I changed it. Good catch!!
I don’t want to derail the thread, but just a heads up: the layout is very broken on my phone (iPhone). The text is clipped on the left side which basically makes the article unreadable!
Oh, and a minor typo: This lets you confidently This way you can confidently....