Exactly what constitutes a "restriction" would seem to be a gray area. Obviously, IBM's lawyers think that ghosting the recipient doesn't count as a "restriction".
First, the GPL gives you rights to the complete corresponding source code of the software you have in your hand RIGHT NOW. It _explicitly_ says you are not entitled to any warranty or support on that software (though it may be "provided for a fee"), nor does it say that you are owed any _future_ versions of that software. Indeed, the GPL says that a user exercising source rights can be used as grounds for ceasing warranty/support (section 6, paragraph 6, IIRC).
Secondly, just because you have the right to do something doesn't mean you're obligated to exercise that right. (Otherwise I could demand that *you* provide me with the source code for the GPL software you received from someone else. Telling me to go pound sand isn't automatically a GPL violation!)
Thirdly, It is not a violation of the GPL to place conditions on on something the GPL explicitly says it doesn't cover.
So, no, it's not a grey are at all. The FSF and others (SFC) don't _like_ this, but they all agree that it's kosher. Note that this isn't a _new_ problem; this has been the basis of Red Hat's business model going back over twenty years now, ie well before the GPLv3 was drafted. Before that, this tactic was used by Cygnus with GCC (ie an actual FSF/GNU project!), starting a few years before the GPLv2 was drafted. Instead of taking steps to close this "loophole", If anything, the language permitting it has been _strengthened_ in each successive GPL version, making arguments about how this is somehow a violation of the "spirit" quite silly.
(Because the alternative is to _require_ Free Software authors to provide warranty and support to everyone, forever, effectively for free. Don't worry, various national legislatures are trying to make that a reality)
Of course IBM's lawyers will probably win the argument in court given their funding, but their circumventing the original intent of the license via a technicality does not give you any good reason to be so sanctimonious about Red Hat's derived work.
Hey, you're the one claiming that you're somehow entitled to permanent access to Red Hat's derived work.
But no, Red Hat's lawyers will win this argument because (1) they have literally centuries of contract law on their side, and (2) they are *correct* and consistent with the law and letter (and spirt!) of the GPL. Ironically, folks that are arguing that Red Hat is in the wrong here are themselves taking a position that violates the letter (as well as the spirit) of the GPL.