"GFDL requires that you name at least the five primary authors." That's misleading. GFDL requires you name at least five of the primary authors *on the title page*. It *also* requires that you name "the authors" (presumably, all of them) on the page entitled History.
No. "History" is an invariant section, and the standard wikimedia copyright statement says that our work is released under the GFDL with no invariant sections. Also, section 4(b) of the GFDL states that an author may waive their right to be listed as an author on the title page. We encourage people not to invoke this right. We also don't go out of our way to alert them that they can. Also, if you treat wikipedia as a single work (ie, a complete encyclopedia) then the title page for all of wikipedia would only contain the names of 5 authors. I think the board could select an appropriate 5, if there was an issue.
--Andrew Whitworth