Certainly I’d agree that the default UI is a design choice whose purpose is to best present what the player has been led to expect by the advertising. So the blurb might say something like “Zork Lives!” and the default presentation shows the player the classic Infocom style.
But that’s a whole other thing from saying “not a player choice” which I take to mean “user preferences have no place in UI design.”
I know: I’m exaggerating your position to make a point, but not strawmanning it, I hope.
It’s easiest to make the counter argument when it affects disability: so locking players to, say, a poorly chosen palette might mean the game is inaccessible to people who are color blind. Or requiring that all panels be displayed at all times means that the text size can’t be altered – thereby locking out players whose eyesight isn’t 20/20.
But I believe that player preferences below the level of exclusionary disability are valid too. Maybe it’s because I’m left handed, so I notice when programs assume I’m using the mouse with my right hand and use keybinding modifiers predominantly from the left hand side of the keyboard.
It’s even worse with physical technology, of course: I’ve lost count of the amount of time I’ve spent with my big honker crushed against the back of a camera because it’s designed for you look through the viewfinder with your right eye. But software is able to be more flexible and accommodating, if we let it, and we shouldn’t wilfully discard that.
We authors are naturally controlling beasts: we had an idea, and we’ve put in a lot of graft – time, energy, skull sweat and even money – to realize that notion and communicate it to other people. We don’t want players mucking it up!
It can be hard to let go and allow players to participate in their own entertainment. 
So I agree: the theme of a game, its style, and its UI are interrelated. It’s a good idea to spend time specifically thinking about that (as we’re doing here.) But in my opinion it’s a bad idea to rigidly enforce it.