They could have been anywhere on the map. They could have said that the Cataclysm pushed them southward, simple. They chose to place them near Northrend because they wanted to bait people with the cheap Wrath nostalgia but also didn't consider that they would be making a Revamped Northrend expansion down the line.
I'm sure the executives will be delighted that they now have a lorefriendly reason to cut costs.Sometimes, different lands can share similar aesthetics...
That's what makes a world a world.