Ah, ok I see the point you were making 👍, for this series wanted to keep it as simple as possible, themes seem to add too much, but are certainly a great next step lesson.
An alternative to setting the Background color is Project Settings -> Rendering -> Environment and change the Default Clear Color to your desired color. If you need different scenes with different background colors then this isn't the solution, but if your project has a uniform background color it can be a quick fix.
