It's a baby bird thing Being slightly squashed from above, means being protected.
I have my chicks in a small aviary, as long as I move slowly, they don't seem to worry about my presence at all. They don't move away from the door when I open it to feed them. The parents come over to check me for bugs, if I sit too still. But I have their 2 older sisters in a cage, they seem more nervous - they hide at the back of the cage when I open it. And I have their 4 older brothers in a larger cage, they are more nervous than the parents but at least one of them will eat seeds from my hand. I'm not entirely sure whether the difference between the 2 females and the 4 males should be attributed to cage size or sex, but I think the cage has the most impact, as the parents in the aviary seems to be equally tame regardless of sex. So you might want to consider a larger cage, to make them less nervous about your hand.