Hopefully I can summarize.
WotC publishes the D&D SRD, and offers to license the work to anyone out there under the OGL. Alice publishes her own game based on the D&D SRD, Elves and Elementals. By doing so, she accepts WotC's offer, and this forms a contract between WotC and Alice, where WotC is the licensor and Alice is the licensee.
Evil Hat publishes the Fate SRD and also offers that work under the OGL. Bob publishes his own game based on the Fate SRD. By doing so, he accepts Evil Hat's offer, and forms a contract between Evil Hat and Bob, were Evil Hat is the licensor and Bob is the licensee.
At no point did WotC become a licensee of Evil Hat's Fate SRD. The WotC/Alice contract and the Evil Hat/Bob contract are independent, even though both the D&D SRD and the Fate SRD are both licensed as OGC under the OGL. WotC would have to do something (e.g. republish) the Fate SRD to accept Evil Hat's offer.
In order to comply with the OGL, Alice and Bob must each offer their own OGC under the OGL for use by other people to use. Just as WotC is not a licensee of the Fate SRD, WotC is similarly not a licensee of Alice's or Bob's OGC unless Wotc does something (e.g. republish) that would constitute accepting the offers from Alice or Bob. There is no automatic pooling of all OGC making everyone a licensee of everyone else.
(edits for clarity)