Oracle - the ZFS/BtrFS connection
Oracle launched the development of BtrFS and supports it in their Red Hat clone.
Oracle controls the licensing for ZFS, and is actively preventing it from from reaching Red Hat.
Oracle has issued XFS patches (toward dedup), and is likely extremely familiar with Red Hat's position.
Red Hat has removed BtrFS to compromise Oracle's clone.
I am guessing that Red Hat wants either a) Oracle to contribute more to Red Hat for BtrFS support (in terms of cash, code, or both), or b) Oracle to release ZFS under a compatible license.
Oracle distributes a "Red Hat-compatible kernel" which might now be stripped of BtrFS. There are likely ways around that, but it forces a divergence which is to Red Hat's liking.