As tigressjewel pointed out, originally
Disneyland was referred to as The Magic Kingdom. Maybe that's more difficult to understand since you didn't grow up going to Disneyland, but there was a point when it *was* commonly referred to by that name.
While WDW *is* most frequently referred to by that title these days in advertisements (and by people who frequent the park), to quote Wikipedia "The Magic Kingdom is also a reference for every Disneyland Park around the world."
Also, not sure if you've been to Disneyland Paris or not, but I'm guessing you haven't. The vast majority of things in the game, all the way down to the images of the different lands used in the backgrounds for the fireworks game, are nearly identical to the Disneyland Paris versions of things. So I'd hardly say that WDW (alone anyway) is supposed to be the "real version" of VMK.