They also lack the ability to whack-a-mole people legally sharing source code with distro maintainers. Their only way out is to close-source all of RHEL, which, good luck re-writing all that GPL code... not gonna happen. Not to mention, even if they did, they'd end up in a compatibility nightmare, where they're constantly fixing packages when GNU diverges from what they've done internally, or package maintainers intentionally making it difficult to run their packages on RHEL-OS, which will absolutely happen given the amount of bad blood they'd create from all that.
This move is clearly to make it more difficult for Oracle, and I'd imagine they'll keep playing nice with everyone else because it's in their best interests to do so.