Section 8 clearly shows that OGC is expandable by future contributors.
What do you mean by "OGC is expandable"? OGC is not a thing that gets bigger or smaller. It's a category of copyrighted material - predominantly text - within a contractual licensing regime.
Here is the text of section 8:
If you distribute Open Game Content You must clearly indicate which portions of the work that you are distributing are Open Game Content.
That is not a definition of anything. It establishes an obligation on parties to the contract who distribute OGC pursuant to the OGL. It applies to the publishers of the Hypertext SRD, who contributes no new OGC, as much as to (say) Paizo, who does contribute new OGC.
Your argument then is, because OGC isn’t a static thing that it’s not defined and thus they can argue it means whatever they want. I find that argument non-sensical because OGC is defined and it’s also clearly expandable within the license as new content creators add to it.
You clearly don't understand my argument.
Here's a question for you. Here is the text of sections 3 and 4 (the emphasis is added by me):
3.Offer and Acceptance: By Using the Open Game Content You indicate Your acceptance of the terms of this License.
4. Grant and Consideration: In consideration for agreeing to use this License, the Contributors grant You a perpetual, worldwide, royalty-free, nonexclusive license with the exact terms of this License to Use, the Open Game Content.
Do the two italicised terms refer to the same thing, or not?
If they do, then the permissions and powers granted pursuant to section 4 are confined to OGC that a licensee uses.
I think an alternative construction is that the phrases are not co-referring, and that the phrase in section 4 refers to
the OGC that occurs in the licensed work. That alternative construction is suggested by section 2, which says that
This License applies to any Open Game Content that contains a notice indicating that the Open Game Content may only be Used under and in terms of this License.
"Applies" is not a term of art, but one way that the licence can "apply" to OGC is to licence its use; and if that is what is intended, then the conferral of permissions and powers by section may pick up the reference in section 2 to
any OGC that contains the relevant notice. This would mean, for instance, that if you publish a work that uses OGC from the SRD, then you enjoy section 4 powers and permissions in respect of the whole of the OGC (ie
any OGC) that is found in the SRD.
Do you have any view on which of the above two constructions is the more plausible one?
Whether or not you do, I also suggest that there is at least one additional construction available of the italicised phrase in section 4, namely,
the OGC that occurs in the licensed work that is offered for licence pursuant to the OGL. That construction would draw even more heavily on the interaction with section 2, and particularly its reference to the OGC
containing a notice that it may only be used under and in terms of the OGL. Because if WotC ceases to offer to license OGC in the SRD, then that OGC ceases to be
OGC that contains a notice indicating that it may only be used under and in terms of the OGL.
You may wish that this third candidate interpretation is not correct. Perhaps its not. But the argument for it is not nonsensical. It's reasoned by reference to the text of the contract. That's how contractual interpretation works.