For those in the field, is this surprising? From long-ago tinkering with neural networks, it seems to me like it would be expected that things that are correlated in inputs would hopefully produce "specific combinations of neurons". But how does it seem to those working actively on it?

Also, is calling them "concepts" a bit generous? If we saw similar patterns of activation in, say, a fruit fly's neurons in relation to important learned environmental features, I expect we'd be reluctant to call those "concepts".