How do I add a scene to the build without it being loaded automatically?

I have added a scene to the build window. When I launch the game - it works great! Only the first scene is loaded. Then I finish some configurations in my Launcher screen, then hit "Load" to load my managers, then LoadScene additively to add the scenes the user requested. *somehow* it's loading scenes that were specifically not requested to be loaded, but existed in the build. WTF?