Even if Trudeau learned the definition the morning of, it speaks well of his background in engineering and math that he was able to assimilate such information and reformulate it coherently. Presenting a technical subject at just the right level of sophistication for a given audience is an invigorating intellectual exercise.
I don't think the limiting factor here was the intelligence of the audience, given that he was presenting at the Perimeter Institute.
That being said, I agree completely on your first point, and it's incredibly refreshing to see a politician make an effort to learn about a technical subject.