Now this is just my opinion and nothing else. Nature has a way of balanceing out animal population. I think it has more to do with hen to roo ratios than it does with pointy eggs or magnets. Put yourself in the position of a hen. She lays the eggs and is the one getting harrassed by the roos. Now if that roo is giving her more attention than she wants, it would stand to reason she might want a few more hens around to take the load off herself. In this case, she might be more inclined to lay pullet eggs to hatch out and give the roo something else to chase around the pen. On the other hand, lets say that there are way more hens than one roo can satisfy. In this case the hens might lay a few more roo eggs to increase the chance that she might get a little more attention. One thing I have noticed with my own eggs, but not really documented, is we seem to be hatching more hens than roos. I keep all of my hens to roo ratios at 4 hens to one roo and so far it seems we are hatching out more hens than roos. I also have one coop that has 8 hens and one roo and these hens seem to produce more roos than hens. Now I dont know if this is coincidence or if there might be something to this balanceing act of nature. Anyways, just thinking out loud.
