As far as JSON, this is the part that's telling to me: "without using a lib/wrapper that hides the underlying implementation." It sounds like he's arguing about generating it directly and parsing it by hand, although without context, I can't say for sure. If that's the case, I'd say the old fart is right on this one.

As far as facts, if you know a lot of facts, you can reason about how changing one fact (eg, "we write this value to this SQL table here, and we are going to stop doing it") allows you to reason about how other facts are affected ("Modules X and Y expect that data to be there").