That isn't what I'm arguing; of course we must know how to use our tools. If that requires also understanding implementation details, even trivial ones (e.g., "it's a DAG"), or if the interface and words used to describe the usage are non-standard, awkward, or worse act to obscure what is actually going on, the tool and/or its documentation is poor.

For example: in this case, knowing what a branch is, how to create and delete one, and how to merge with one is necessary. Knowing that the branch identifier is a hash, called a "reference" or similar jargon and what that entails, internally, is superfluous and adds pointless complexity: if that's really required then git isn't good. I have more important things to think about as a developer than what internal machinery operates git.