> as opposed to interactively querying the terminal for its capabilities somehow

Querying terminals, in the 1970s when there was a Cambrian explosion in terminal capabilities, with tens of different manufacturers?

Even if you could have gotten all of them to agree this was necessary, I think nobody could afford to put the smartness for such a protocol in their hardware. Hardware was expensive in those days.

You read the opposite of what that post is saying. It says a fixed DB was okay in the 1970s, but not in the 2020s.