Yes, actually it is how it happened. WotC never released the SRD, it was done by 3rd parties under OGL. Why the hell would WotC give out an edition for free (other than being idiots in how the OGL was worded)?
My point was mostly that WotC wasn't responsible for the SRD. Yes it existed. Yes it was free.
First, let's get something straight. Wizards did indeed release a
d20 SRD for 3.5. It had to. The 3.5 PHB has a copyright notice explicitly stating that there is no Open Gaming Content in the book. It was in all of Wizards 3.5 D&D books, except two that I know of. Generally, this was Wizard's MO, release a book with a copyright notice denying there is any Open Gaming Content. Later, they might add in the content to the SRD. If you look at the link I provided, there are elements from the Expanded Psionics Handbook and Deities and Demigods in the SRD, despite those things not being in the 3 Core Rulebooks.
Now, about those two exceptions. First in Monster Manual 2. In MM2, Wizards reprinted two monsters from a non-Wizard's source, to promote the d20 license. The monsters appeared in the back of the book, with a plain white background and none of the normal MM trade dressing.
The second exception is a lot closer to what you are talking about. When Wizards release Unearthed Arcana, the copyright notice stated the book was Open Gaming Content, except for a things like trade dress, registered trademarks, and a few notable monsters like the Beholder. That content is not in the 3.5 SRD. However, online SRDs like
The Hypertext SRD included the Open Content from UA.
Edit: Ninjed!