Sigh...
Look, I asked the question, which you very deliberately chose to not answer. Why, out of all the illogical things in D&D, do you care so much about the perceived lack of logic in a couple of backgrounds?
Which is why I brought up fighters and weapons. It's illogical that every single fighter, ranger, paladin, and barbarian should all happen to know how to use every single weapon with equal proficiency, regardless of the characters' wealth, training, access to materials, and any differences in the societies where they grew up.
By the rules, you could have a character have been a penniless urchin who never wielded anything bigger than a knife and who came from a society where only the military was allowed to wield swords and yet not only know how to use a broadsword, but probably be better at using it than a soldier (soldiers in the MM only get a +3 attack bonus). And you would allow it without blinking an eye.
Yet the idea that an NPC might travel and end up in the same place as a PC is just too far, even though it might only happen once in a multi-year campaign, if that much?