IIRC, Redhat also made it more difficult to make a RHEL clone in order to neuter Oracle Linux and other possible RHEL clones and the sponsoring of CentOS was to have a cost-free RHEL clone in their direct sphere of influence.
That was to make it harder for Oracle to offer support for OEL, but made no difference to Centos & the non-commercial clones because they shipped the RH kernel unmodified and didn't need to worry about what any individual patch did.
I'm not sure its been a thing since RHEL6 either.