Subscription example not behaving like it should

import { EventEmitter } from "events";
import { initTRPC } from "@trpc/server";
import { observable } from "@trpc/server/observable";
import { z } from "zod";

// create a global event emitter (could be replaced by redis, etc)
const ee = new EventEmitter();

const t = initTRPC.create();

export const appRouter = t.router({
    onAdd: t.procedure.subscription(() => {
        // return an `observable` with a callback which is triggered immediately
        return observable((emit) => {
            console.log("running");

            const onAdd = (data: any) => {
                // emit data to client
                emit.next(data);
            };

            // trigger `onAdd()` when `add` is triggered in our event emitter
            ee.on("add", onAdd);

            // unsubscribe function when client disconnects or stops subscribing
            return () => {
                ee.off("add", onAdd);
            };
        });
    }),
    add: t.procedure
        .input(
            z.object({
                id: z.string().uuid().optional(),
                text: z.string().min(1),
            })
        )
        .mutation(async (opts) => {
            const post = { ...opts.input }; /* [..] add to db */

            ee.emit("add", post);
            return post;
        }),
});

console.log(ee.listeners("add"));