Hi @lnelson,
Welcome to the Auth0 Community!
What you have observed is to be expected since importing users are considered existing users. In other words, there is no user creation happening.
Moreover, the Post-User Registration Action triggers during the authentication pipeline, whereas the Import/Export extension does not, and is a dashboard feature.
In this scenario, you could generate and send invitations to these users to reset their passwords on your app.
Please let me know if you have any questions.
Thanks.