We have orgs/MSSP that run some Connectors which ingest Alerts on behalf of different customers. two examples:
- a mailbox that multiple customers forward emails to (e.g. phishing@mssp), this is Exchange connector
- a connector to an old shared SIEM that is not multi tenant (no customer access allowed), but a MSSP is routing inbound SIEM-SOAR alerts into the MultiTenancy
In these cases the Connector has 'Environment field name', which allows the Connector to analyse a Key of the inbound alert, and the associated Value is compared to the Alias field you point to above.

It's a feature for specific use cases, and is not used by the majority of customers.
HTH
Andy