Does user get's created on auth0 as well after creating on some external db through custom create database script

I have a requirement where I need to create user on some external portal through API, when user is created on my website. And on login, I again have to make a call to that external portal to get a user token. To implement this, I have enabled this option - “Sync user profile attributes at each login”.

When I am trying to create a user from auth0 dashboard, my Create Database Action Scripts is successfully creating the user on external portal, but user is not getting created on auth0. Is this expected or am I missing something here.

As mentioned in the comments of the script, I am returning this after successfull sign up on external portal.
callback(null);