Even if you suppose that Git had some extreme UX overhaul to the point of renaming builtins like "branch", the existing names would still survive in the popular

Even if you suppose that Git had some extreme UX overhaul to the point of renaming builtins like "branch", the existing names would still survive in the popular zeitgeist, as they predated Git. So, I think it's an interesting thought experiment, but practically speaking a non-starter. You'd never be able to fully migrate over, instead it would be another case of that xkcd about N standards.