Well, _if_ they will still be pushing everything they're doing "upstream first", then you are right, I have no use for their "secret patch combination" and they can keep it secret. But in that case it makes even less sense to keep stuff secret in the first place, because anybody with a specific interest can almost trivially reconstruct their patch combination.
As others have commented, this whole policy will only inconvenience CentOS and SL lightly, and maybe Oracle a little bit more. I'm concerned it will be quite annoying for Fedora-only devs, though.
Overall I have the feeling this will mostly inconvenience legitimate uses of the RHEL kernel sources, while not really making life harder for the "illegitimate" users (as RH management defines them). I'm open to be proven wrong, though.