"DXM does nothing", proceeds to link a study whose contents describe significant decreases in cough severity versus placebo.
I am convinced that many people ask LLM's "give me a citation URL" and don't bother to read it.
It's the same people who just googled a couple keywords and used that as a citation without reading the link, pre-AI.
I read the main section of the lit review linked by OP, and it didn't seem to come to any real conclusions.
> The results of this review have to be interpreted with caution because the number of studies in each category of cough preparations was small. [...] There is no good evidence for or against the effectiveness of OTC medicines in acute cough.