It's a single package with relatively few additions, mostly color schemes in CSS.
Anaconda documents this in /usr/share/branding
RHEL puts a lot into subpackages of redhat-releasea
But it isn't really the point. There are thousands of packages. Only a handful actually deal with branding. I was an engineer at Red Hat for 7.5 years, and I left last June. I'm intimately familiar with this, and while it's more complex than sed, it's much simpler than it sounds, and the CentOS people are definitely familiar with it. Branding is NOT their hurdle. It's the build system, as they repeatedly mention.
You're blasting Red Hat for making it seem like they're somehow opposed to clones. That's fatuous. A major engineering company with complex workflows uses their own build system. News at 11. They also make this free and document the hell out of it. Anyone who has ever built a package for Fedora is familiar with it. Anyone who has ever dealt with release management/engineering for a product inside Red Hat is extremely familiar with it, and that includes many of the core CentOS team, plus the Fedora RelEng SIG is easy to join if you want to learn. It's complicated, but it's not black magic or even hard information to get. CentOS ALREADY USES IT.
It really doesn't matter whether the RHEL image is "for development use only" (you didn't want support anyway). Stop moving the goalposts.
* Debranding is much more work than a single RPM. https://wiki.centos.org/About/Building_8