unintended map transition

[Azure Nova]

The first 'hidden' square of the underwater's hidden pathway to a secret "cameo" dungeon, you can map transition down into a map that doesnt have any other entrances and exits, and looks like it shouldn't be accessible. there are only 2 tiles you can walk on anbd can only return the way you came
https://steamcommunity.com/sharedfiles/filedetails/?id=3301050719
https://steamcommunity.com/sharedfiles/filedetails/?id=3301051704