Considering that benzodiazepines can be found naturally in the plant kingdom it is reasonable to say it can be in the natural products. It does not mean they repackaged a pharmaceutical or putting drugs in their products. Many of your 'drugs' came from plant sources, so its safe to say these active ingredients will be present especially if thats what the product was being used for.
Benzodiazepines can be found in some natural products. This particular one, however, is not a naturally-occurring one. It's chlorinated, and very few natural products contain organochlorines.
When drug companies take drugs from plant sources, they isolate the compounds that are physiologically active. Then they check to see how well it works, what dosages are required, what side effects are present, etc.
When this is done, they look at the chemical structure of the compounds, and make a list of other compounds that are structurally similar- replacing a methyl group with an ethyl group, changing a carboxylic acid into an amine, acetylating a hydroxyl group, putting a chlorine where there was originally a hydrogen, that sort of thing.
Then they test all of these derivatives. Some of them will turn out to be better than the original. Many of them will turn out to be worse. Some of them turn out to be effective against a completely different disease.
But none of these derivatives will be found in the original plant matter. So if a "herbal remedy" pill contains one of these synthetic derivatives, then you know it's been spiked.
If your willow bark tea contains ASA in addition to the complex tannin salicylate naturally found in willow, it didn't get there naturally.
If your "100% Natural Milk of Poppy Sweet-Dreams(tm)" tablet contains heroin, it wasn't put there by the poppy.