But the enterprise version is the open source version. Red Hat just didn't provide the binaries, now they even provide the binaries (since they acquired CentOS). Since White Box Linux, CentOS, and Scientific were started (which was pretty quickly after they launched enterprise Linux), they have been selling per-machine support and 'blame us when it does not work' licenses.
A similar approach may have worked, but it is not a given. Red Hat and SUSE arrived on the market when there we no big open source support companies. Once containerization turned out to be a good idea, the other open source companies could quickly adopt and provide support contracts for the same tech (which they have done).
CentOS can be used for whatever you wish, but that's not a RH binary of course.
That said, it is in RH's best interest to have a free version of RHEL that customers can try out and migrate their workloads to, precisely because it's easy to migrate them to RHEL. So yes, in that sense, there's some relationship.
You're correct though that there's a lot more relationship than I previously thought. Thanks for the link! I'll update my knowledge :).