We got a change through only six weeks ago - added in the waterfall ends on our bench. I reckon they agreed to is because it was a $3k change, if yours is a small change I think they will stick to their antiquated way off thinking.
I agree that they need to look at variations, you make your decision at pre start (in our case) some five months ago and in a hurry. If something isn't available then they are super quick to make a change that you have to cop, but I don't see why that can't be reciprocated.