Thinking about that quote, it sounds nonsensical

At the outset, all businesses seek to grow faster than the average/stock market. Five years later, half will do better than average, and half will do worse than average.

Saying that the half that did worse should have instead invested into the market, five years ago, is kind of meaningless.

Dedicated incremental static type checkers for dynamic languages already exist. In particular, Pyright for Python is fantastic and in many ways surpasses the type systems of classic typed languages