It's only irksome to you because you've learned the incorrect definition (incorrect, at least, according to the orginal definition when revolvers were created).
"Things are what they are"? No, they are what they are NOT, when you refuse to call a revolver a pistol, in accordance with its original definition, as revolvers being a wholly-encompassed subset (type) of pistol - a revolving pistol. You're using circular logic, which is a flaw. That's like someone saying that when you call a clip a magazine, you're irking them, because they know that the detachable thing that holds cartridges surrounded on 5 sides by metal is a clip, not a magazine, and YOU learned it wrong, not them. Circular.
I guess there's really 2 questions: (1) What does a reputable dictionary say the definition is (such as Oxford's); and (2) IF Oxford's says that a pistol is a semi-auto or derringer or single shot or bolt pistol, but not revolver, THEN should we or should we not try to buck that definition in order to make it evolve BACK to its original definition. I say that we do buck back to the original def!
Don't get me wrong, 45 Fu, you're RIGHT about what the dictionary says, IINM, as definition number "1". I believe that it is only the secondary definition of pistol that shows it synonymous with "handgun". But this is vice versa of how it was in the past. Somehow it changed in the last 80-100 years.
