Just tested on a fresh install of 4.2. Both var_dumps echo null for me. Your question needs more context (likely some more code) to be able to be resolved.

AntonNiklasson said:

There might be an active session causing this. Try running Auth::logout(); before creating the user.

Hmmm I have a feeling you are right here because I dont check the Auth state when doing a registration (ye I know I should). Ill redirect the login and registration page if a user is logged in and tell them to log out first. Ill also make sure on a new registration I run the Auth::logout() as a safety catch. This solution makes sense so ill investigate and mark as solution if its correct :)