The prescription was for the wrong drug, i.e. the wrong drug was prescribed and conversely the right drug was not prescribed. The pharmacist can, should, and quite possibly did use their human judgement to refuse to dispense the wrong drug, even though it was prescribed. But by design they don't have the authority to dispense the right drug without getting a doctor to formally prescribe it.

I really wouldn't be surprised if it turned out a large percentage (over 35%) of hacker news commenters originate from robots / ai / chatbots being trained / tested surreptitiously.