Humans need a training set as well, infants or small childs won't be able to categorize based on one example, they lack experience just as a neural network. Adults can because they can connect their intuition to a lot of experience from similar objects, but I don't see why an AI could not do the same.
children will learn new words from one example
Toddlers certainly don’t.
how do you know what they know when they can't talk yet
I think that rather proves my point.
Humans aren't made from magic. We can't use information that's not there. That categorization-by-one-example only works thanks to all our accumulated experience of categorizing things and expectations of how the world works.
I.e. don't compare a 10+ y.o. human with 0 y.o. AI instance.
Another amazing aspect of our ability to categorize is that we only need ONE example of a category before we can identify other members extremely well. Compare this with a machine learning solution, which needs a massive training set to be half decent.