The article is extremely short, but comparing 2-4 OTC doses of diphenhydramine to a level of alcohol concentration above what constitutes a DUI in most places seems like an odd choice? Or is that just a matter of proof of concept, go for the big obvious demonstration first?
Having done that for awhile once? It basically is, and that is the typically OTC recommended dose.
They also sell 1-gram extra-strength Tylenol pills OTC, but that's a very high dose for an average person. And what do you know, acetaminophen is the leading cause of acute liver failure in the US.