Also read that a hen can store and or reject sperm from the roo and she "decides" to fertilize the egg.Your Welcome!
The ZW genetics is very different. It makes Rooster important since they have a bit more genetic material passed on.
It also explains why you can have more males to females sometimes. Just like men having only Girls, Hens can lay more male eggs than female. To figure this out, you need to figure which Hens\pullets are laying more of one gender or the other.
This is why fermented feed, temperature and other environmental type of methods, including the shape of the egg will have little to do with the gender of the chicks. The Hens eggs are either male of female from the very beginning--before the pullet even hatches.