Enabling an IPMI policy, whether it be on traditional UCSM managed blades, standalone CIMC, or IMM based ones, accomplishes the same thing: allows/enables CIMC response to IPMI over LAN, establishes IPMI username/PW, etc.
Example of IPMI use: RedHat & Oracle 'Fencing' using IPMI to shutdown or restart a host.
https://intersight.com/help/saas/resources/cisco_intersight_managed_mode_configuration#supported_ucs_server_policies
Creating an IPMI Over LAN Policy
"The IPMI over LAN policy defines the protocols for interfacing with a service processor that is embedded in a server platform. The Intelligent Platform Management Interface (IPMI) enables an operating system to obtain information about the system health and control system hardware and directs the Cisco IMC to perform required actions. You can create an IPMI Over LAN policy to manage the IPMI messages through Cisco Intersight."
Kirk...