He wasn't claiming you were stupid or uneducated, just that you didn't understand statistics. The fewer times you try something, the less accurate your predictions will be. If you craft 20 items, and 10 are doubled, that does not mean doubling has a 1/10 chance. It just means you were unlucky. However, if you craft 10,000 items and get 1,000 doubles, there's a much greater chance that it really is close to 1/10.
I've never taken a statistics course either. You don't need a class to know a thing. A class will just give you a much deeper understanding of that thing (if you have a good teacher, and are good at learning from teachers).
While it's a kind of funny story, I don't think education has anything to do with map rolling skills. Lots of people are good at lots of different things.