You do bring up an interesting point. It sounds like GG is basically using OGL to PREVENT anyone from using their content, which is a behavior that would certainly NOT be possible under a CC license! This sort of flaw would also exist in ORC if it provides a similar type of clause, effectively a dominant publisher can force you to either be 'incompatible' (at least in terms of terminology, which means a lot to gamers) or else pound sand.
From my own perpective, I don't really see this as a problem, because I've understood the OGL worked like that since shortly after it was first published. That's a part of the agreement, and not some loophole someone has discovered and is attempting to use years later. One of my own first thoughts were that I could claim my spell names are PI, allowing the reuse of the mechanics but not the names themselves, if I didn't want people making something compatible with my work.
The OGL does not promise everything made under it will be compatible with everything else, or even imply creators have any moral responsibility to ensure that. It simply lets you contribute some game mechanics (or, really, pretty much
anything you want) to a central "pool" that any other OGL licencee can draw upon. I've seen plenty of products where the only OGC was the stuff
they had reused, and honestly don't see any real problem with that because I've never read the license to imply that was a requirement. Much of the reason for this is because the d20 Trademark License
did specifically require that you have a specific amount of Open Game Content, so anyone who was there at the beginning and read the both alongside one another could notice the omission of such things in one and the inclusion in the other.
I don't see this as a flaw. I see it as a reason why multiple types of license exist, to suit the needs of the person releasing material under them. If someone
chooses to use the CC license, then yes,they have to grant those extra rights. The choice, however, needs to be the original creator's.
I am far more concerned with holding people to the license they have chosen to agree to (mainly WotC), than with an ideal of "everyone working together". I
like the idea of the latter, but I'm going to be far more judgemental over people with the former.