I think breck's point is that, since many jurisdictions in the world grant authors inalienable rights over their works that cannot be waived nor transferred by any means (e.g. some "moral rights" in France and maybe other European jurisdictions are unwaivable), no license ever makes a work "100% free".

Which is true, but not spelt out clearly by breck, and it's kind of annoying for it to be phrased by breck in a way that leaves unclear whether it's merely a semantic nitpick or an actual suggestion that the author should've done something more to waive rights over the work. (I don't think it's the latter; I'm unaware of anything more the OP could do to "fix" this "problem" other than kill himself, and I'm not certain if even that would be sufficient in all jurisdictions.)