Complete BS. (Told youThanks for the info, I just tried calling my local London Apple Store and the guy I spoke with said they only get stock of the custom models when someone returns an unwanted order from online. He wouldn't check either which was annoying.
If I pass one I will stick my head in and try my luck.
But when you insist that the Specialist actually checks on their iPhone thing you'll see they're there. Here's the receipt for mine as proof!

"Oh that's the first time I've ever seen that!", they'll say. Every. Damn. Time.