All I want to say about the new issue is that a small fractional increase in size for a large collection of manuals is not a big deal. That's not enough to make a license non-free.
The GFDL, however, places *no* restrictions on the number or size of Invariant Sections, either absolutely, or relative to the size of the manual. Remember the hypothetical "emacs reference card", which must be accompanied by 12 pages of additional invariant material? Sounds like a big deal to me. While the case of a particular manual might be a "small fractional increase", in general the GFDL allows for unlimited increase. So I guess you're saying that each GFDL'ed manual would have to be evaluated on a case-by-case basis to see whether it was free. (Not so with the GPL.)
I have been trying to convince Debian developers that the GFDL's methods are proper, but you're all entitled to form your own opinions and make your own decisions.
As are members of the FSF and contributors to it, I hope? We have been trying to convince *you* that the GFDL's methods are improper.