Comment by sbf501

You are correct, with a subtle modification: there are a "Close Window" and "Exit Application" mode in some popular X-based windowed apps (see: VSCode). Some apps, like Eclipse, solve this by hosting the child windows in a parent container. But then you lose screen real estate.

But you always need ONE child window open or it will exit entirely.

MacOS has a different approach, where the application top level process keeps running, even if it has no windows, but this requires some sort of GUI element to communicate with application.