To fuel your theory the hen does determine sex of the chick before the egg is ever fertilized by a rooster. Hens tend to lay the same shape of an egg each time, we can often tell which hen laid an egg by shape as well as color or size if you only have a few hens and there is a regular...
That's been around a long time. One of the ancient Greeks wrote about it, I believe it was Aristotle, though he thought the pointy eggs were pullets and the round eggs were cockerels. Exactly opposite to today's wisdom. It's so simple you wonder why the commercial hatcheries don't use it...