I agree completely...Sorry to hear about the cockerel . Most hatcheries claim 90% accuracy on sexing . Some are hard to sex but I think a good sexer can beat 90% . That said cockerels are a loss for them so $ says 10% cockerel is a probability . Free chicks also likely cockerels . All about $ .
Years ago I ordered 100 cockerel Cxs I ended up with 10 pullets in the bunch.
The next year I accidentally ordered 100 pullets.. I received 100 pullets and no cockerels..
With cx they make more on the cockerels and the females are their loss ...