Correct. There’s no OOP inheritance going on. Game objects in Defold are by default empty “containers” with a transform (position, rotation and scale). You can attach one game object to another so that the child game object inherits the transform of the parent.
Game objects become something useful when you add components to them. Components can be sprites, labels, scripts, sounds etc.
Side-note: In the editor and the data files there is also a concept of collections. A collection is a way for you to organise groups/collections of game objects. These groups of game objects can be spawned using factories or loaded and unloaded when needed. The collections themselves do not exists in runtime. It’s only the game objects that are there.
Learn more here: The building blocks of Defold