[buttproblem]

While I agree with you, it is better to focus on practical things other than pedantic names, you can really notice the difference more when you look at the foundation of Go's language level concurrency paradigm.

Concurrency in Go is based on Communicating Sequential Processes (CSP) by Hoare; this was originally published in 1978. Reading CSP you see all the ideas are abstractly formalized in math terms: there really is no notion of multiple streams of execution occurring at the same time (i.e., multiple hardware threads). So, a distinction is made between things cooperating (concurrency in their parlance) and things running at the same time (parallelism).

To continue this idea, parallelism, again using their terms, really is an implementation of the more abstract concept of concurrency. That is, given a description of concurrent processes communicating you can run them in parallel (and reason about their correctness).

If you do not make the distinction, regardless of the terms you use, you remove the layers of abstraction necessary to reason about complex systems (separation of high level concepts and their implementation).