This is probably because you are not connected to the Cloud Functions emulator.

You should be able to use the blocking function by running the following code (I did):

import { getApp } from "firebase/app";
import { getFunctions, connectFunctionsEmulator } from "firebase/functions";

const functions = getFunctions(getApp());
connectFunctionsEmulator(functions, "127.0.0.1", 5001);

cf) https://firebase.google.com/docs/emulator-suite/connect_functions#instrument_your_app_to_talk_to_the_emulators