I agree that straight run should be as hatched and by nature should run close to 50/50,but................... think about this. Most people are buying chicks to become laying hens. Even though straight run is cheaper to buy, most will order sexed pullets. If the hatch starts out at 50/50 and the majority of females are pulled out to fill pullet orders you now have a mix that is maybe 80/20 or worse. And that is 80% male! So in effect "straight run" orders can be almost all male. Not very good odds if you are looking for cheap layers!
If straight run is done right, it means that the chicks are blindly pulled from the bin to fill your order. What you get depends on the odds. Since the hatch should be 50-50, some people think what you get should be 50%-50%, but odds don't work that way. For example, using four chicks as a base, the odds are:
4 roosters - 1 in 16
3 roosters and 1 pullet - 1 in 4
2 roosters and 2 pullets - 3 in 8
1 rooster and 3 pullets - 1 in 4
4 pullets - 1 in 16
So the odds of getting 50-50 are less than 50%. I've personally gotten 7 pullets from an order of 6 straight run. Even the packing peanut was a pullet. But someone somewhere got 6 roosters from an order of 6 straight run. I'm sure they are convinced that the hatchery is unethical.
Just like the rest of life, some hatcheries may be more ethical than others. It is very possible that some pull the pullets before they start pullling the chicks to fill an order. It is also possible that some don't.