Isn't it the case that, when someone posts content to Wikipedia, they
are releasing it under GFDL, regardless of any other license they may
also choose to release it under? So, even if the content in question
were clearly labeled as CC-BY, CC-BY-SA, or even CC-BY-NC, it is also
released under GFDL. With the exception of putting something into PD
(or some other less restrictive license than GFDL), it just doesn't
matter what other restrictions may be claimed, it is still released
under GFDL. Excepting, of course, content posted without the knowledge
or permission of the copyright holder.
Given the way you say it, I would say yes...