It’s basically the opposite. Fedora is the community based upstream, and some of it reaches RHEL, but Fedora isn’t Red Hat.
What Red Hat did was limit who they distribute the source code to to paid customers, and add provisions to their TOS to give them the right to end their paid contract with you if you redistribute it. You aren’t prevented from doing so, but choosing to do so prevents you from getting future versions, which you were only entitled to through said contract. They also still open-source to CentOS Stream, just upstream of RHEL.
Now, do I think it was a good move by RH, no. Was it legal, probably, yes, but IANAL, eventual courts will tell. Did it go against the “spirit” of the GPL, maybe, yes. But is RHEL closed-source? No, it’s objectively not. Please, don’t spread misinformation.