Oh good, now that I know the truth I can sleep again! Sure would've been a good place for an easter egg though (albeit one that nobody could uncover).
Indeed. Consider if the game had used a method similar to Adventure's...where simply moving to the right is not enough to uncover a secret room (the dot must also have been moved out of it's starting screen). The game could have had
such a triggering mechanism to eliminate the "invisible barrier" very easily if the programmer had wanted - just ignore the game world map and check if the criteria has been met (such as specific objects in inventory).
Fortunately, this "special exception"-type code is usually pretty easy to discover via disassembly (Adventure's "move right" code is longer than any other direction). Without stumbling upon such a trigger, one might never discover such a secret simply by playing the game...or even by hacking the horizontal location variable to blink yourself there
In this case, the "non-secret" revealed itself purely by chance when just hacking the variable. Disassembling the game is the only way to be sure of anything.