Earlier quoted context omitted.
I can see how the evolutionary advantage of such hardened eggs would be huge!
Evolved so they *only* hatch after passing through the digestive system of a waterfowl might be a good evolutionary trick to avoid inbreeding. Your eggs won't hatch until they're well away from your relatives.
I will add new genetics to the line soon, for what it's worth. It isn't an experiment to see what will happen. In most cases I never expected them to breed to begin with.