To me, this feels the same as saying Sonic Colors Ultimate is open source because it was made with Godot. The engine is open source and making the game is left as an exercise to the user.
But you have all the assets of the actual finished game as well as the code used to run it, using your example. You don't get the game dev studio, i.e. datasets, expertise, and compute. Just because someone gives you all the source code and methods they used to make a game, doesn't mean anyone can just go and easily make a sequel, but it helps.
