Hum, a wild supposition. If the chamber is oval, then the fired brass would be oval also. Easily seen by looking/feeling, confirmed with a micrometer. Knowledgeable person would know that and wrote that in the article as proof.

More likely this a either an oversized chamber or undersized brass or accumulation of both. But I have not examined rifle or brass so my supposition is speculative and not knowledgeable either.