FrogReaver
The most respectful and polite poster ever
That notice is at the top of SRD 5.1 though.WotC fails to satisfy the bolded portion of section 2.
2. The License: 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. You must affix such a notice to any Open Game Content that you Use. No terms may be added to or subtracted from this License except as described by the License itself. No other terms or conditions may be applied to any Open Game Content distributed using this License.
WotC does not post the notice that they must affix if they were using the OGL. Since section 2 is the license, they do not use the license when putting out content.
Permission to copy, modify and distribute the files collectively known as the System Reference Document 5.1 (“SRD5”) is granted solely through the use of the Open Gaming License, Version 1.0a.