No, the size of egg also changes with size of the hens body.. what would that say for all pullet or bantam size eggs verse mature or large fowl sized eggs?
The size of the egg does effect the size of the chick.. Smaller eggs hatch smaller chicks. Bigger eggs hatch bigger chicks. They will still meet their eventual genetic potential size.
Of course in that gender prediction theory.. which is still hogwash.. "they" may be talking about the relative comparison size of the egg from the same individual hen. This is in line with the pointed verses rounded theory.. which also has nothing to do with gender chromosome inheritance.
I predict chicken chicks in both genders. And note that pictures are
rarely worth a thousand words.. those *look* like Silkie eggs.
For hatching purposes.. eggs *should* be about equal size/color so they have ABOUT the same amount of evaporation. With that said.. I have totally (and regularly) hatched Silkies with Marans and others.. with large disparity in egg size... but with my incubation parameters dialed in..
With all that said.. I'm not here to be right, I'm here to have fun, share, and learn.. here's a couple links that support your theory, one fun discussion and two more technical..
https://www.backyardchickens.com/threads/does-egg-shape-determine-gender.1515820/
https://www.scielo.br/j/rbca/a/wRXK...ngth was considered,the sex of hatching chick.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9832119/
I will note on the back side of this.. I have seen evidence that incubation temperature effects viability of which gender is most likely to survive.. meaning that one or the other doesn't make it to hatch.. not that the gender was changed by such conditions. Gender is determined by the hen before the egg is laid. I've personally had power outages and temperature spikes.. and still gotten 50/50 results.
Happy hatching!

