Does IPAM even belong in holistic DCIM?

Yes, because IPAM is important for the entire data center operation, because

• the network is the basis of all communication and processes in the data center / company
• IP addresses / hostnames are required for identification in comprehensive troubleshooting
• IP addresses are part of the configuration of active components
• Reservation pools and an overview of address allocations are extremely helpful for planning and avoiding bottlenecks

Conversely, IPAM itself also requires sub-disciplines of DCIM, such as

• Mass operations and work orders from process management
• customer-based billing and relationships from Business Service Management (BSM)
• standardized interfaces and ETL mechanisms for integrating DDI tools
• relationships to objects from other management areas for the organization of new network structures