In order to just remove it, technically speaking they needed
permission from EVERY SINGLE CONTRIBUTOR,
That's the same as the situation for any change between licenses. For
instance, if Apache wanted to relicense under the GPL, they would need
permission from EVERY SINGLE CONTRIBUTOR. That would cause practical
difficulties if they ever wanted to merge Apache with some GPL-covered
program. Worse practical difficulties, in fact, because that can't be
done at all without a license.
This problem is unfortunate, but no worse in the case of two ways of
using the GFDL than with a pair of two different free software
licenses.
