This would be closer to a bug-for-bug compatibility issue, as a result of an implementation change on the infra side of things. It's not due to the OS which is bug-for-bug compatible with its origin, RHEL 8.
While it would be nice if EL7 stacks are considered by the rebuild distributions, it's not a requirement and they are free to use features supported by the platforms they're building.
https://access.redhat.com/articles/rhel-abi-compatibility
https://access.redhat.com/articles/rhel8-abi-compatibility
https://access.redhat.com/articles/rhel9-abi-compatibility
This would be closer to a bug-for-bug compatibility issue, as a result of an implementation change on the infra side of things. It's not due to the OS which is bug-for-bug compatible with its origin, RHEL 8.
While it would be nice if EL7 stacks are considered by the rebuild distributions, it's not a requirement and they are free to use features supported by the platforms they're building.