Hi! I've searched the internet, and the problem is that RPG Maker has an autotile system, which "knows" how to choose a tile even if you only have the corners.
But I am not using rpg maker, it is a game made in godot. It doesn't matter... I'll use the ones that work for me and that's it. thank you
Okay! I'm not familiar with godot but yes, RPG Maker uses autotiles. It's a little complicated to create but they work well when it comes to setting up on a game with this editor / engine.
By the way, I hope you enjoy the tileset on your game! And if you need anything else, don't hesitate to ask!