Doc the return

src/vector/app.tsx

@@ -167,6 +167,10 @@ export async function loadApp(fragParams: {}) {
             idBaseUrl: config['validated_server_config'].isUrl,
         });
         PlatformPeg.get().startSingleSignOn(tempCli, "sso", `/${getScreenFromLocation(window.location).screen}`);
+
+        // We return here because startSingleSignOn() will asynchronously redirect us. We don't
+        // care to wait for it, and don't want to show any UI while we wait (not even half a welcome
+        // page). As such, just don't even bother loading the MatrixChat component.
         return;
     }