I couldn’t find a discussion of this in my references so, I can only speculate.
Because birds often use them as perches, the bent flowers may have developed that way from perching birds. If you see a pattern, such as many flowers all bent the same direction, suspect the prevailing winds have done some bending. This may occur especially when the cattails are young and green.
Another possibility is lack of water, which may cause some curling effect during development. When water returns, more flexible leaves can straighten themselves, while the cattail flower might not. Some insect feeding may cause distortion, too, as it does on the leaves and flowers of other flowering plants. Thrips cause distortion when feeding, and some flower thrips are found on cattail.