It's not unexplainable. Any init by design is supposed to spawn new processes with the given environment, permissions, capabilities. When you run "your-init-cli

It's not unexplainable. Any init by design is supposed to spawn new processes with the given environment, permissions, capabilities. When you run "your-init-cli start foo", you're starting a new service process. run0 is just one step away from that, because it connects the terminal to that process. It's less "a new thing has been created with systemd" and more "a user interface was exposed for an existing functionality".