Ah, there is a logical fallacy there. That logical fallacy that is just because they reused the same bitkeeper word that they took it from there AND are using it in the same sense. Ultimately this is a strawman, you are putting Bitkeeper's practice and arguments onto git.
That’s fair, but the OP’s conclusion had no supporting premises at all.
Ultimately this is a digression; this change is being made not because of the intentions of the authors of git, but to be considerate of users of GitHub.
Slave is never used once in git documentation, never has been and never will be: https://git-scm.com/search/results?search=slave