While multiple studies comparing several encyclopedias are mentioned, they tend to have small sample sizes (only a few articles) and being on par with other encyclopedias doesn't necessarily make Wikipedia reliable, it could just as well be that the other options are similarly unreliable (it seems like all studies found something to criticize).
Additionally, I interpret "Wikipedia's information about pharmacology was 99.7% accurate when compared to a pharmacology textbook" to mean that the pharmacology textbook was taken as the gold standard and Wikipedia got pretty close. But 3 errors per 1000 (whatever their unit of measurement was) might not be reliable enough to be used by pharmacologists.