I don’t understand your concern with this clause. Just because you have a license to use a copyrighted work does not mean that you have a claim of ownership or exclusive usage of that work.
The copyright holder of a work is the owner of that work. The entire basis of the GPL relies on copyright principles and applicable copyright law, and copyright principles and law are based on the concept of ownership of intellectual property.
Note that such clauses do not preclude you from claiming ownership of any modifications you make to someone else’s copyrighted work; rather, it stipulates that you cannot claim ownership of the modified work as a whole.
I don’t see any problems here.
EDIT
let’s take an actual example, plugin X is released under GPL, Y gets it, modifies the author, auhor uri, name and so on, it adds the copyright notice of X author in license.txt, makes some modifications to the plugin, realease it under GPL.
In this case, X is the owner and copyright holder for the original work, and Y is the copyright holder for the derivative work. Note that Y only has ownership of his own modifications, even though he holds the copyright for the derivative work. In this case, X still owns the original work, and retains copyright and ownership of both the original work and any part of the original work incorporated in the derivative work.
Thus, Y can only claim ownership of his own modifications, rather than on the derived work as a whole, because the derived work as a whole incorporates work owned by X.