The argument doesn’t attack the companies themselves; it only rejects their claims.

This describes how the author rejects a claim (that ginseng counteracts effects of stress) as untrue despite only citing the fact that scientific studies haven’t yet verified it. Although the claim hasn't been shown to be true, this doesn't prove that the claim is false.

The argument doesn’t draw an inference from a sample, but instead cites the lack of definitive evidence for a claim.

This is irrelevant. The author concludes that ginseng doesn’t relieve stress. People’s reasons for drinking tea don’t matter.

The author only rejects the companies’ claims that “ginseng counteracts the effects of stress”, so it wouldn’t matter if any other ingredient does.