This isn’t scaremongering where synthetic drugs are commonly sold in shops where they’re competing with non-synthetic drugs sold on the street, and constantly dodging regulation by reformulating every time a formula is classified.
This was not scaremongering, I bought some myself. Twice.
I have connections with people in the old synthetic cannabinoid industry and know how cheap that shit is to buy and how easy it is to order from China, so I don't see in any way it being a stretch of the imagination to envisage people growing poor quality weed and adding to it.