I don't see how the two bolded bits fit together.
But assuming the second one is correct, that fits with what I said to
@Paul Farquhar upthread: there was a licence in place. There is no basis I can see for inferring from the existence (past or present) of that game that WotC does not enjoy IP rights in respect of various aspects of the D&D game system.
This claim isn't true. You can see for yourself at this link:
Here's the section 15 statment:
System Reference Document 5.0 Copyright 2016, Wizards of the Coast, Inc.; Authors Mike Mearls, Jeremy Crawford, Chris Perkins, Rodney Thompson, Peter Lee, James Wyatt, Robert J. Schwalb, Bruce R. Cordell, Chris Sims, and Steve Townshend, based on original material by E. Gary Gygax and Dave Arneson.
The whole text of the SRD is copyrighted in favour of WotC. The SRD also contains product identity, called out in a statement at the front of the document, which WotC claims to enjoy trademark or similar rights over.
Yes. Green Ronin owns the copyright in that text. It is obliged to do so (or to enjoy a licence over the text) by section 5 of the OGL, before purporting to publish it as OGC:
If You are contributing original material as Open Game Content, You represent that Your Contributions are Your original creation and/or You have sufficient rights to grant the rights conveyed by this License.
That claim is too simplistic. And even where rules or processes are not themselves protected by copyright, the text in which they are stated can be. The text of the SRD is copyright WotC. The text of M&M is copyright Green Ronin. Etc.