Through the years Weatherby has outsourced manufacturing of some product lines to others who branded the product with the Weatherby name. That is why there are some Weatherby products showing made in Germany, Japan, or somewhere other than Paso Robles.
Does your shotgun say "Made in Japan"?
SKB manufactured shotguns for Weatherby beginning in 1984.https://www.skbshotguns.com/about-skb/the-skb-story
The diagram matching and the SKB parts number matching seem like more than a coincidence.
If it does not fit return it. Certainly seems worth a $28 gamble.