It's a thing, it's called food fraud. Happens commonly these days with various spices, which are often cut with metals to increase their weight. Sometimes those metals are heavy metals, which are obviously bad for you.

Historically this happened to basically all food. Meat was sold rotten, meat was pumped with water for volume, people lied about what meat they were selling, meat was glued together with other meat to create reconstituted cuts that were sold as whole, and on and on. We had exposes, The Jungle, and now that basically doesn't exist because of the FDA.

But, in countries without an FDA equivalent, you can imagine that food fraud runs wild. It ran wild in the US, too, and I think it's fair to say that the only thing limiting it isn't morals, it's the FDA and regulatory framework we've built.