> When someone writes about a function argument I immediately know that code gets executed, but when someone talks about a parameter I know that he’s looking at some declaration or definition!

It might not lead to something being done incorrectly, but I do think it can make communication easier. My initial opinion was that the author was being pedantic, but the above example changed my mind. I've actually had conversations where this distinction would've made everything simpler.

It always matters. The difference between argument and parameter is the difference between concrete and abstract, or the difference between contents and container. Would you ask whether those are relevant distinctions?

Most things rarely matter always. The purpose of words is generally to convey an idea to someone else. Humans are very effective at filling gaps or patching over mistakes in the communications they receive. There are certain key aspects that determine the meaning of a sentence, and one can get pretty far by getting those parts close enough. I would param that the distinction between "argument vs parameter" is hardly ever a key aspect in a specific communication. The terms you mentioned are more important, so I don't the analogy quite holds up.

If the speaker used argument or parameter incorrectly, the context would make the intention very clear. Most listeners would make the correct mental association without even thinking about it.