For a filesystem I'd worry about what that implies for testing, especially for enterprise hardware and workloads. RHEL has significantly more users and it seems likely that their users would have more diversity than just Oracle shops.

Are you completely forgetting SUSE? They’re a thing, too, after all.

Not forgetting them or Oracle but RHEL has something like twice the marketshare of the two combined. I'm not sure I've ever seen a support matrix where either of them is listed but RHEL is not, whereas the reverse is not uncommon.