Stink bugs have propogated their way across the USA in the last 5-7 years, and there's a variety of other bugs, fish, crustaceans, and even rodents that are prevalent that simply didn't exist here a decade or two or three ago.
Obviously some are accidental stow aways in cargo ships etc, but all of them? Why not force your enemy to deal with a common plague that your country already has?
That's seems like a bs cover up story, they could've sent anything even empty packages for that "narrative". They're could've definitely been nefarious intention behind the seeds. Whether it be a hyper invasive species, mites, bugs, possible blight, other disease, etc...