Rounder is supposed to be female while pointed is male, but considering your hen lays reletively the same shape of an egg you'd have to consider (since the female determines the sex of the egg) if a hen that lays rounder eggs has a higher average of producing females and a hen that lays more pointed eggs has a higher average of producing males. There are some people and I can name one that has been playing with this theory by incubating the more rounded eggs and she has been having a higher pullet ratio.
Personally I think it's all wishfull thinking. I've had a 100% hatch rate hatched at the higher average and the majority (for once) was pullets. Not by much though.