OK, I'm seeing where you're coming from. But I guess I don't see the severity. Yes, git's terminology is highly non-orthogonal (the umpteen different synonyms for the "index" was pretty amusing). But... that's just the frosting. Who cares how messy it is if the cake is still good?

Yes, it's messy. But I don't really see that it hurts comprehension. And it hurts learning only inasmuch as you can't guess at a command and have to check the man page (i.e. I know there's a diff variant that checks the index vs. HEAD, what's it called?). I can't honestly say I found it difficult to understand what the index was due to this.