I think the point is basically "unless there's a good reason for your API to look different than your DB schema, ontologically speaking, then the schema has alr

I think the point is basically "unless there's a good reason for your API to look different than your DB schema, ontologically speaking, then the schema has already effectively defined your API and just let people interact with the DB", or, alternatively, "bake in as much of the data constraints as possible into your DB schema, and only when you can't enforce them with column constraints or DB extensions should you add APIs on top".