> Particularly with reference to "a human drug"

Veterinary drugs are a thing, and it appears the FDA regulates them, too:

https://www.fda.gov/animal-veterinary/resources-you/fda-regu...

Human drug it’s just a drug. Only if it’s not ‘human’ you have to specify.

That's certainly true if you're an ordinary person.

If you're the person who writes press releases for an organization which regulates both human and animal drugs, then you have a reason to be specific.

Purchasing over the counter animal drugs for use in humans is somewhat common in prepper communities. Perhaps the wording was aimed at them.