Sample proof of https://docs.godotengine.org/en/stable/tutorials/scripting/singletons_autoload.html

This project shows how to use a Singleton script game_state.gd

The script loads once, and prints "Game State Ready".

Then loads main.tscn which main.gd prints "main".

Then in main's ready, it just changes to not-main.tscn.

At which point, "Game State Ready" does NOT print again, to show that it's only loaded once.

"not main" then prints, from the not_main.gd ready function.