It’s pitch is a little different, it gives you ‘Workspaces’ which are somewhat connected, and tools to manage big deployments.
IBM, Oracle and many large companies use it because 100,000+ participants in one workspace is quite unmanageable.
Think channel namespacing whilst unifying user provisioning and enabling DM and MPDM across the entire company. Users can have access to one or many namespaces, they sign in once and it populates all enabled workspaces into that users client.
You can share channels between workspace within Enterprise Grid fairly trivially (although this now works between Slack tenancies owned by different companies too!)
Still runs on the same infrastructure in AWS as other Slack customers though.
From a policy perspective you can push down settings to all Workspaces in your SEG, and define whether you “centrally control” or “delegate to Workspace owners” on a setting by setting basis.