FWIW, the "pencil" moniker as descriptive adjective refers to being long and thin.
Like "pencil neck" "pencil skirt" or "pencil jeans".
None of those things look exactly like a pencil either but the adjective is applied to them anyway.
As for "bull" barrel, I've seen that adjective applied to fat untapered barrels my whole life - whether it is precisely correct or not it gets the idea across.
To me it is about communicating an idea - that is the important thing. More important than nit-picking other people's terminology.
Maybe I'm just "different" that way.
