In the settings example the app.restored Promise is resolved before getting the settings : extension-examples/index.ts at 8bc09d2839efed8078c9fbc43da0fd39a0b7d0a3 · jupyterlab/extension-examples · GitHub
It is my understanding that app.restored resolves after all the extensions have returned or resolved. However, if ISettingRegistry is specified as a requirement, then why do we need to wait for app.restored?