To avoid too many AXI adapters in different places, it would make sense to keep all adapters in one location. Integrating the narrow_adapter into chimera_cluster_adapter is the last step, as far as I know. This avoids excessive adapters being instantiated and used throughout the SoC design. Prefixing narrow_adapter to chimera_narrow_adapter also helps avoid name conflicts with other IPs.
As discussed in #24 (comment)