The owner of the pistol might have originally bought it as a decoration piece, which does not require proof in any CIP signature country, and subsequently requested it get proofed so that he could shoot it. Unfortunately it failed proof. It being private property, it was returned to the owner with a failure certification. It is not the property of the Proof House.
The thing that concerns me about this is that ALL firearms are VERY closely inspected BEFORE proofing is carried out - this is the 'primary view. THEN it is proofed, and having passed proof, gets the appropriate stamp, but only after another close inspection has been carried out to ensure that there is no residual damage resulting from the proof test. Of course, if there is any damage, then it will have failed proof.
Dr Németh is not a panic-monger, nor is he underly-generous with the truth, as you seem to imply in your post. He is a highly-regarded senior lecturer on military history in an important university in Budapest and a leading light on BP shooting of all kinds in his native country and internationally.