Amad, can you explain where the SimpleTemplate came from? Is this some automation in the backend? Where do we define this template? I am little confused here.

Specifically here:
This results in a PnP device rule created on DNA Center. The rule was created by the user, the state is planned (which means the device has not initiated communication yet), and there has been no contact. It also specifies the workflow for onboarding “simpleTemplate”.