wp_login hook not fired?

No that hook is not triggered because unfortunately it’s coupled to all sorts of login functionality that shouldn’t run when you just switch from one user to another, including session management, redirects, and particularly two-factor authentication plugins.

User Switching fires its own hooks that you can use though. Details here: https://www.ads-software.com/plugins/user-switching/#are%20any%20plugin%20actions%20called%20when%20a%20user%20switches%20account%3F