Satisfying the hunger for type safety?

Tom Adriaenssen riffs on the id subset in show me some id:

Let me explain: even though you might assume that all those objects are actually going to be DataPoint objects, there’s no actual guarantee that they will actual be DataPoint objects at runtime. Casting them only satisfies your hunger for type safety, but nothing else really.

More importantly, it only seems to satisfy your hunger for type safety, it doesn't actually provide any. It's less nutritious than sugar water in that respect, not even calories, never mind the protein, fiber, vitamins and other goodness. More like a pacifier, really, or the product of a cargo cult.