(I said "Can't they think that they really are impostors?" but I should have said: can't they admit that they really are less talented than they sometimes think?)
I know that I am a talented (but slow) writer (in my language), and good at creating allegorical ideas, but still I often feel that I am stupid. When I feel so, do I say to myself: you suffer from the impostor syndrome? No. I say: if you were much, much more intelligent than you are, you would have already solved many of those problems that you have created for yourself.
And when I say that I am a perfectionist, I know that I am still very, very far from any perfection, maybe I am just in the beginning.