It sounds like they're talking about "GitHub Enterprise Cloud with Data Residency." This is a separate product to the standard "GitHub Enterprise Cloud" (including Enterprise Managed Users) which runs on normal github.com infrastructure.

If you have a Data Residency tenant, you access it through an endpoint like octocorp.ghe.com

GitHub seems to try to use specific language here to avoid this confusion, because they are quite different products, but it seem to me they were named confusingly in the first place...