If publisher X uses the OGC of publisher Y and changes it a bit, that new, changed bit is not by default OGC. You seem to think, and repeatedly insist, that it is OGC...but it is not. That's never been how the OGL worked. Whatever content the publisher makes OGC is all that's OGC. If someone wants to stand on the shoulders of OGC and not release their stuff as OGC, that's entirely their choice. You and I agree that they should, but there's nothing in the OGL that requires them to. The CC-BY license is far more open than the OGL.
Actually, most derived OGC is OGC per default,
as most of it is what is described as "game mechanics". Per 1.0a section 1(d) this is per default OGC. The way that maybe might prevent such from being ogc is to argue they embody product identity.
And thus is the beauty of it! While it might not strictly speaking legaly bind you to share alike, the only way of avoiding it is to put explicitly on paper that you dont want to give this to the community. This is not looking good, and quite obvious. Hence as long as there isnt a conspiracy starting to exploit this in a way that normalises it, the PR risk of not sharing alike is normally just more than what you can expect to gain from holding on to the IP - unless it is already well established reasonable product identity like a "Jedi" class.
Thus this soft SA has indeed been extremely succefull in making a great effectively SA arrangement.
(I have to add that I am not convinced it is not actually legally SA, but this post is written under the assumption that the essence of the post I reply to was correct)