It's weird how the glitch lets you get off the path on the overworld. I've done Super Mario World hacking before, and I know that there are Layer 1 levels stored in most spots before the Layer 2 levels kick in via unlocking their paths. 90% of the unused overworld levels are just duplicates of the bonus room because any undefined level is automatically set to Level 0, which is the bonus room. All the overworlds are connected (when you go through the "loop" on the right side of the Special World you actually go through Vanilla Dome. It doesn't show you in Vanilla Dome because you didn't go through an exit tile) so you're probably just accessing a level on another overworld that you didn't unlock yet.
Here is some more information on those levels. Keep in mind that there are also many other levels not accessible from the overworld, such as the level that contains doors to all the boss rooms.