It doesn't say it's the only place you can purchase it in the world, it's just talking about the US. It says it's a limited and exclusive pressing of 2,000 discs exclusively for Record Store Day in the US. If someone wanted to buy it at another time, they could have searched for it this whole time and paid for extra shipping and handling from the UK and if they miss out on this it's still available. But if not, this is a good opportunity to buy it at a much cheaper price.

It's a much better deal for the buyer outside the UK and UK buyers most likely already know about this because it's sold and has been sold at a major retailer for a long time so it doesn't seem like much of an issue at all. It's a very US centric promotion and therefore that's where the focus of the text and information is.