How often do the cousins of Louis the 5th of France impact on coding decisions? I can't see the argument for a completely generalist model being best for _coding_ in all situations.

They probably don't. But some words acquire their full sense meaning from historical and-non-programming context.

Words that are or were fairly common in tech circles — "bailiwick", "gatekeeper", "daemon", "boundary", "infer", "method".

It's true to say that most of these words have some specific meanings in tech, but you don't necessarily want the LLM to have only those narrow meanings when you are talking to it. A broader grasp of the word means the LLM won't go down a specific pathway before understanding you by analogy. That broader grasp comes from non-programming understanding.