Or else, if the post is talking about a "public-facing API resource", can someone tell me why the API wouldn't implement querying for multiple of the same record type at once? It just seems to me that choosing between getting 1 owner, and "get ALL owners" (as TFA puts it), is like a law of the excluded middle
It's tricky because in some cases you might be able to batch all the queries up front, but in others you will only know the IDs you need to fetch after you get one or more intermediate results back and apply business logic to arrive at a decision.
As of today there's no silver bullet beyond having a solid and principles-first understanding of your database and related infrastructure.
This might be true for some APIs but if you're letting the caller control what they fetch, you don't really have that luxury. An extreme example is Graphql-based APIs but even Rest-based APIs might allow some flexibility to decide what they fetch.