It’s more than a packaging format but yes. It includes all dependencies needed to run the main program in a container but the kernel. It’s a complete separate root filesystem. When you run it, as intended, a single process is started which loads all the things it needs from that filesystem. It’s isolated from the rest of the system unless you share resources with it, like directories or special devices. Obviously this results in larger packages but there is a clever way to save on that overhead with layering, so in practice while still significantly larger than single program deb files, it’s not nearly as bad as it sounds. The thing is that Flatpak and Snap also package dependencies to a different degree.