By that logic all sorts of technical and scientific terms would be "meaningless".

Seems like playing semantics, to not say disingenuous, using "meaningless" to mean "unknown", when the former clearly has a negative connotation.

Most technical and scientific terms absolutely are meaningless outside of related technical and scientific communities. All terms have at least one person who sees it as meaningful else it could not fundamentally exist as a term, but clearly the context is about trying use it in contexts where the audience is the general population. There is no shared understanding of what it means in that setting, thus it is meaningless (to that audience).