It sounds a fantastic claim, but I'll read up a bit on it so thanks.
Must admit though I've not had any drug - prescribed or illicit - that had a more immediate and powerful effect on my anxiety than a benzodiazepine (granted I've not tried heroin before!).
Thankfully they are incredibly hard to get prescribed where I live due too all the above associated dangers.
https://pmc.ncbi.nlm.nih.gov/articles/PMC12500767/ - this is the study the GP is talking about.