Somebody sounds as cynical as I am about many things. It is possible that a hatchery would do something like that. If they did that would be unethical.
21 out of 27, that is 78% males. My incubator hatches are typically in the 20 chick range. A few times I've had hatches where 75% have been either male or 75% female. It seems like half the time the split is 2/3 - 1/3 and could go either way as to sex. One time I even got 7 pullets out of 7 straight run chicks, from Cackle. Could have just as easily been seven cockerels. To me that is just the odds and somebody has to hit those odds occasionally.