I think you are imposing an unnecessary interpretation. They made both names and flavor text closed, as was their right, because both of them had copious amounts of world-names and descriptions in them. It was easier to do a blanket cut-off then to delineate with each monster. But their monsters are fine, and (with some minor tweaking) very usable. I've used them in at least two different assignments.
I do not feel they have the moral right to put an undead ooze under the OGL and claim we don't have a right to call it an "undead ooze". The idea is risible. And "undead ooze" was not something that randomly fell under their restrictions; it was their choice of example.
There's an important part of sharing where the community builds a commons, a set of useful material that everyone knows and understands. Monster-wise, in 3.x, that was the SRD monsters and the Tome of Horrors monsters, maybe the Monster Geographica (which was pretty late). It was not the Creature Compendium, as monsters that have no name and no description don't exist. I suppose it might be a nice collection of mechanical bits for some, though I don't understand why, but it was not really an addition to the commons.
I notice you again interpret in the most uncharitable way possible. I think the better explanation is that they worded their statement poorly; but essentially all the mechanics of the book are going to be open, and all the fluff text is going to be closed. People learned how to say this more clearly as time went by, but you should make allowances for a learning curve.
I can't assume that "All game mechanics and statistics derivative of Open Game Content and the System Reference Document are to be considered Open Gaming Content." really meant "All game mechanics and statistics are to be considered Open Gaming Content." That's not being charitable; that's rudely putting (or, in this case, removing) words from their mouths because apparently they didn't know better.
To be honest, I have no idea what your complaint about the Paizo declaration is. I think its a model declaration. Clear, comprehensive and generous.
One of the problems I see with the OGL is that this is considered a model declaration. The Creature Collection had a fairly model declaration for clarity: The OGC material is "all creature statistic templates from Size Type (e.g. Small Undead) down to Advancement Range, and all Text under the "Combat" header of each creature's section (except the creatures name or proper names specific to the Scarred Lands setting.) It's pretty obvious what is OGC with that. The question, in Paizo's declaration, of what is "dialogue, plots, storylines, locations, [or] characters" has been the source of lawsuits. And this is on the PRD, which should be 100% OGC.
Edit: To be fair, the Paizo declaration is fairly clear on second glance. But is
The Egyptian Mythos on D20PFSRD really okay?
The OGL did what it was supposed to
And I think other publishers should think about whether what the WotC needed for D&D is what they need for their system. I maintain that the CC-BY and CC-BY-SA are easier to use and clearer about what is actually free, that the CC-BY is better in practice for most case (wherein publishers who want to contribute back can use the CC-BY to do so) and the CC-BY-SA is much better if you actually want to compel that new work be added to the community.